Making Bubbles with Metal Oxides

Today’s chatter is about making bubbles inside kiln-fired glass using metal oxides rather than borax, bicarbonate of soda or other commercial bubble mixtures. I hope you find it a productive distraction, especially if you’re getting tired of being in a “covid-19 lock-down”.

And before I start, what I’m talking about in this blog works for microwave kilns as well as for “proper” glass kilns.


Looking Backwards

Way back in 2013 I posted some related chatter in Bubbles – Borax or Bicarb? about some early experiments with borax and bicarbonate of soda, trapping them between layers of glass to create bubbles, rather than using commercial bubble mixtures.

The problem you are likely to encounter with borax and bicarbonate of soda is that the size and quantity of bubbles that get produced is difficult to control and that simply producing bubbles inside glass is not especially exciting.

Today’s chatter takes this bubble production story forwards by exploring the use of metal oxides which not only produce bubbles but also to tint the glass that’s trapping the bubbles.


Some Technical Background

Necessary conditions to produce bubbles between two pieces of glass are that

  1. we must be able to fuse two pieces of glass together before the chosen chemical substance breaks down, and that
  2. when the substance breaks down it will produce a gaseous substance that can form bubbles between two layers of glass.

Both these conditions explain why borax was not very effective. As noted in my Bubbles – Borax or Bicarb? chatter, the problem was that the water of hydration for borax gets boiled-off at around 75°C, long before the surrounding pieces of glass are soft enough to fuse together at somewhere around 500°C. The sparse bubbles produced with borax are produced at a high temperature when the borax undergoes another change. If you want to better understand what water of hydration means, and also have some fun, then I recommend you look at another of my chatterings from 2013 called Science Meets Art – The Borax Bead Test.

By contrast, I found that bicarbonate of soda was better able to produce copious bubbles, because it decomposes into sodium carbonate  at about 50°C, loses water of hydration at around 100°C, then it breaks down some more at a high temperature, possibly around its melting point of 851°C, and certainly well above the temperature at which the two layers of glass have softened and fused together.

So, we now know what to look for when considering metal oxides that might produce bubbles between two pieces of glass in a kiln. We want it to break down and produce a gaseous product at a temperature that’s higher than the softening temperature of the glass we’re using but lower than the maximum temperature our glass kilns can achieve.


Some Lateral Thinking

In the main, though not exclusively, it’s metal oxides that are used to produce coloured glass and it’s often those same metal oxides that are used by potters for their coloured glazes. So, a metal oxide used to produce coloured glass or as a pottery glaze is worth considering.

We can refine our candidate metal oxides by considering “colour chemistry”. It is rather interesting to realise that metal oxides used to colour glass, produce colour pottery glazes, the pigments in paints and the colour effects in fireworks will all produce the same colour (or sometimes a range of colours) given the same metal oxide. So, for example, using copper oxide tends to produce a turquoise blue coloured glass just as it produces a turquoise blue firework.

We can continue the colour chemistry thread by considering scientific diagnostic methods such as the flame test you probably did at high school and the now rarely seen borax bead test. Both methods produce characteristic colours for different metals. Incidentally, you’ll find my “take” on the borax bead test to make little antennae and flower stamens here.

In the context of glass manufacture and pottery glazes, these metal oxides are subjected to very high temperatures compared to what we would normally use in a glass kiln, and in those contexts the aim is to “develop the colour” rather than “generate some bubbles”. So, we might expect some of them to not work at the lower temperatures we use with ordinary glass kilns.

So, our task is to look for metal oxides that are used by glass manufacturers and potters that might break down at a reasonable fusing temperature into metal and oxygen gas. The liberated oxygen produces the bubbles. The metal diffuses into the glass to produce a characteristic colour tint that depends on the metal that’s involved.


Three Candidate Metal Oxides

I have already mentioned the creation of bubbles with borax and bicarbonate of soda, and they aren’t metal oxides, so I will not mention them again. Instead we will focus on just three metal oxides that I have experimented with, for no better reason than they’re the ones I’ve tried and tested.

If you have heard of the paint pigment and glass colour called “cobalt blue” then you’re already ahead of the game because you already implicitly know of at least one metal oxide that can be used to produce a colour. The cobalt blue colour is produced by the breakdown of cobalt oxide in coloured glass manufacture and pottery glazes. This is what is supposed to happen to cobalt (II,III) oxide at 950°C according to Wikipedia:

2 Co3O4 → 6 CoO + O2

Similarly, turquoise blue is produced by the breakdown of copper (II) oxide in coloured glass manufacture and in pottery glazes. This is what we hope happens to copper (II) oxide when it is heated:

2 CuO → 2 Cu + O2

And as a third example, you may have heard of the “chromium green” or the old name “viridian”. Here it is chromium (III) oxide that is used in glass manufacture and pottery glazes as well as a paint pigment. This is what happens to chromium (III) oxide when it is heated:

Cr2O3 +3 CrO3 → 5 CrO2 + O2

In each case we are hoping, with fingers crossed, that the oxygen-liberating decomposition will happen at a sensible fusing temperature. Of course, I already know which of them will work and which one of them doesn’t. With this little teaser you should now be in a mild state of excited anticipation, are you not?

If you enjoy researching on the Internet, or know a wise and friendly potter, you’ll maybe want to explore the possibilities of other metal oxides that are used in coloured glass manufacture and as pottery glazes. Some of your discoveries might be suitable for use in a glass kiln but others might require temperatures far higher than we would tend to use in a glass kiln. Perhaps the easiest way to do your research is to make friends with an experienced potter and start by asking them about the coloured glazes they use at lower pottery-firing temperatures.


Using the Metal Oxides

Just as it was way back in my Bubbles – Borax or Bicarb? chatter, the basic concept is that we sparingly apply some of the chosen metal oxide between two layers of glass and heat the whole assembly to a full-fuse temperature to cause the bubble effect and colour diffusion. But simple concepts usually hide little tricks and nuances that need further exploration. Life is never so simple…

For your initial experiments I suggest you make use of a clear glass base and a clear glass capping layer, otherwise you will not be able to clearly see what you achieve in your experiments. Later you can experiment with coloured base glass and maybe some tinted capping glass.

Start with your piece of base glass. It does not matter whether it is 2mm or 3mm but as usual we are aiming for a stack thickness of about 6mm.

On the top of your piece of base glass you must apply a very thin layer of your chosen metal oxide. Keep the metal oxide away from the very edges of the base glass and ensure none has found its way onto the sides or you may get undesirable black marks in the finished piece. This picture shows what you should be trying to achieve for a copious amount of bubbling (and you can click the image to look closer).

In the Applying the metal oxide layer section below I will give you some practical advice about how to apply such a nice even thin layer of the metal oxide. The best method I’ve found is not very obvious!

When you have your thin layer of metal oxide on the top of your base glass, and cleaned away any over-spill, place your clear glass cap on top. This picture shows what you should be trying to achieve:

Your test piece is now ready for kiln firing using a typical full-fuse schedule. To some extent the time spent at the top temperature will determine the size of bubbles produced and the amount of colour diffusion.

A longer hold time at the top temperature means more time for individual bubbles to coalesce into bigger bubbles. This is no different than the way as bubbles in a sudsy foam also coalesce over time. And just like the situation with a sudsy foam, bubbles in glass can coalesce to the point when they burst, sometimes leaving a crater.

A longer hold time at the top temperature allows a little more time for the metal atoms to diffuse further into the glass, though the difference is barely noticeable.

Here is a picture of what you should expect to produce:

The turquoise blue example used copper oxide. The deeper blue example used a mixture of copper oxide and cobalt oxide. In the Mixing the metal oxides section below I will briefly chatter about mixing metal oxides and in the Some metal oxides fail section below I will chatter about why you don’t see a picture of a chromium oxide example. Yes, it was the chromium oxide that didn’t work in my glass kiln.

When you come to your own experiments, explore different amounts of metal oxide and vary your kiln’s firing schedule in terms of top temperature and hold time to get a feel for how to reliably get the results you’re looking for. Experimentation is always a key to learning and success!

To demonstrate there are some easy and simple creative possibilities with little bubbles, here are some coasters I made.

The pale blue comes from the copper oxide and the cobalt blue colour comes from a mixture of copper oxide with some added cobalt oxide.


Mixing the metal oxides

I have not had any trouble producing nice turquoise blue bubbles with copper oxide. The only question is how much or how little to use for the size of bubbles and degree of colouring you are looking for. Just a few experiments will tell you how much to use and at what firing temperature. If you use too much then you are likely to produce massive bubbles that either burst whilst still in the kiln or are so fragile after cooling that they easily pop when you press on them, or you will encounter craters where massive bubbles have already popped during the kiln firing process.

Early experiments with cobalt oxide were not pleasing, producing a mess of crazy fizzing and not the deep cobalt blue bubbles I was hoping for. It was clear than using cobalt oxide on its own was not an effective strategy. Further experiments revealed a simple answer to the problem…

To obtain nice cobalt blue bubbles I now use a mixture of copper oxide and cobalt oxide. It takes some experimenting to get the mixture just right but the best results seem to come from mainly copper oxide with just a small touch of cobalt oxide in the mixture. Again it is experiments that lead to success.

The two bubbly glass blobs and the coasters you saw in the picture above are simple examples of what you are aiming for – sensible sized bubbles and a reasonably amount of colour.


Applying the metal oxide layer

It might seem strange that I have chosen to devote a whole section to describe how to apply some black powder to the surface of a piece of glass, but I’m sure you will find my comments and experiences useful.

Copper oxide and cobalt oxide are fine black powders. If you try to apply them to a glass surface you will soon realise that attempting to apply a dry, thin, even layer is very difficult. It is also very messy because these fine powders also have a habit of “getting everywhere” except where you actually want them. So, trust my experiences and don’t try to use these metal oxide powders in their dry form.

An obvious solution might be to mix some of the metal oxide in water and, with a paint brush, attempt to paint the mixture onto your glass. In theory this should work but in practise it is not so good because there are two problems.

The first problem is that the metal oxide powders are suspended rather than dissolved in the water, so have a nasty habit of clumping and settling out. The more serious problem is that water clumps into droplets on the glass surface, just as it does outside you window on a rainy day. This droplet problem is a consequence of surface tension and the solution is to reduce the surface tension by using a surfactant or by some other trickery, but this is a big topic that I will not explore in any great detail. Instead, I’ll just tell you my answer to these problems…

The best solution I found, which allows a thin even layer of metal oxide to be painted onto a glass surface, is to make a mixture of the metal oxide in a weak CMC solution.

But what do I mean by “weak CMC solution” I hear you cry. And why should it be important or useful? Let me explain with a short explanation and references to some of my previous chatterings…

I have mentioned CMC in several of my previous chatterings and have done so because it’s really useful in several areas stained glass crafts. CMC is an acronym for carboxymethyl cellulose and an example trade name for it is “Tylo”. Sugar crafters use “Tylo” with icing sugar to form a sugar paste because CMC can be used to thicken a liquid or to form a stiff gel. In effect it is able to “suspend” water and icing sugar in its tangled matrix. We can do similar things within our craft as well…

As glass crafters we can use CMC to good effect. If you need some convincing then notice that I have chattered about how it might be used to make a safety flux gel over here, how it can be used to thicken glastac into a gel over here, how it could be used to bind together glass grinder waste (or powdered frit) for freeze-fuse work over here and how to squirt powdered frits over here. The last of these is perhaps the most important for you to read because it explains everything you need to know about what CMC is, how it behaves and how we can exploit it for our craft. Trust me, it’s a useful addition to your glass crafting toolkit. And I’ve not even approached the possibility of using CMC with frits to produce powder wafers on a sheet of acetate.

CMC is not expensive and you don’t need much, so get onto Ebay and look for “CMC powder” or “Tylo”. In these “covid-19 lock down” days it’s important to keep the economy ticking over so buy some now!

Back to the topic at hand…

What you need to create is a smooth runny mixture from the powdered CMC and water, then add a little of the metal oxide you have chosen. The aim is to take advantage of the stickiness of the CMC to address the surface tension problem and take advantage of the way the CMC suspends the metal oxide evenly in its sticky matrix.

It takes some experimenting to get the optimum mixture, but when you’re able to apply the mixture onto your glass with a paintbrush you know you’re on the right path. Do remember that in addition to using a “colour wash”, you can do swirls, squiggles or whatever else you might choose to do with the paintbrush. For example the outlines of the hearts in the coaster were done with a fine paint brush.

I store my ready-made CMC, water and metal oxide mixtures in tiny little lidded acrylic pots of the kind that often get used for lip balm. Over time the mixtures will dry out but simply re-adding some water and stirring them back into their original state is all that’s needed.  The pot on the left is ready to use but the pot on the right has dried out.

Some metal oxides fail

You have maybe noticed that I mentioned chromium oxide earlier on but have said nothing more about it. This is because it was a dead end experiment. The chromium oxide did not break down between piece of clear glass even with a hotter-than-usual full-fuse schedule.

So, I was disappointed to find that although chromium oxide can be used to produce green glass (using the pot melt method) and can be used as a pottery glaze, it does not work at the lower temperatures we tend to use with glass fusing kilns.

My philosophy is that we learn more from failures than successes. Maybe you agree.


Buy Cautiously

From my chatter you will now realise that metal oxides used in coloured glass manufacture and for pottery glazes are good candidates for experimentation, but do not guarantee success because we are working at lower temperatures. Implicit in this is a warning not to buy larger quantities of a metal oxide unless you know they will work.

You should now also realise that copper oxide is perhaps the easiest to use and that cobalt oxide can also be used but is best used very sparingly in a mixture with copper oxide. I have a 100g tub of each of them, purchased mail order from my stained glass supplier. But you don’t need this much – I expect to die of old age before I finish using them.  Implicit in this is a suggestion to buy the smallest quantity you can find.

More importantly you should now understand that chromium oxide did not work in a glass kiln, even though it is used in pottery glazes and in coloured glass manufacture. This was a costly mistake because I have very nearly 500g of chromium oxide and no further use for it. Implicit is the warning not to repeat my mistake with chromium oxide.

The key message is therefore to buy only small quantities. If you are friendly with other glass fusers, try to share the cost of buying a 100g tub of copper oxide and perhaps also a 100g tub of cobalt oxide.

Better still, perhaps, is to make friends with your local high school chemistry teacher then ask if you can “borrow” a gram or two of your chosen metal oxide for experimental purposes. Draw them in to your ruse with chatter about wanting to explore colour chemistry, talk about the use of metal oxides in coloured glass manufacture and as pottery glazes. Scientists are naturally curious so exploit their weakness mercilessly!

Oh, and remember to also buy some CMC. Better still, make friends with a sugar crafter, but not until your “social distancing” rules are relaxed. No crafting endeavour is worth dying for!


Unexpected Delights

The small circular blobs of bubbly glass and the coasters I have shown you earlier in those pictures are more exciting than you might suppose. Although they might only look like coloured pieces of bubbly glass, they have hidden delights to bestow.

Hold them up to the sun (or some other kind of bright source of light) and all those little bubbles of oxygen act like lenses, focusing the light, producing spectacular sparkling starbursts of light rays.

You can exploit this sparkly trait by constructing a “watery panel” (ideally slumped over an arch) with fused-on representations of  aquatic plants and fishes over a bubbly blue underwater background and put it in a sunny bathroom window. Or as an alternative, experiment with squiggly brush work and squiggles of glass in a bubbly blue arch panel like this example:

Another hidden delight that the blue bubbles open up a magical scientific story. Tell your friends, and especially children, about how the metal oxide breaks down at high temperatures into metal atoms and oxygen gas. Tell them that the metal atoms diffuse slowly into the glass to create their characteristic colours, the exact same colour that a firework would produce if made using the same metal oxide. Then tell them that the bubbles in the glass contain nothing but pure oxygen, trapped for eternity inside the glass.



It’s time for me to conclude my chattering and I suppose the key things to say are that adding copper oxide, cobalt oxide and some CMC to you your glass crafting toolkit opens up many new possibilities.

Not only will those two metal oxides provide you with a means to add blue bubbles to your creations, the CMC will help you explore the freeze-fuse technique, thicken your glastac glue, and more besides.

And finally, here’s a picture of a silly little piece I made some time ago. It’s a representation of a photograph of an particle collision in a bubble chamber where an atom gets smashed into sub-atomic particles. Glass art can even be made interesting to a atomic physicist!

Stay safe everyone and have a productive “lock-down”.


Posted in Borax, Borax bead test, Bubbles, CMC, Experiment, Tylo | Tagged , , , , , , | 16 Comments

Leaded Light Cement Formulation

The process of waterproofing a leaded glass panel is a time-proven process using simple raw materials formulated as leaded light cement. In this blog I will consider several formulations for leaded light cement and discuss the various constituents that should and should not be part of the formulations.

The object of cementing a stained glass panel is to make the leaded panel weatherproof, to support the glass within the lead framework and to strengthen the whole structure in a way that makes it rigid and sturdy. When done properly the result is a leaded glass panel that could remain strong and weatherproof for more than a hundred years.

Let’s get cracking. There’s lots of chatter to get through and although some of it’s not going to be exciting I can at least promise to try and cover the subject in reasonable depth.

As an aside I apologise for not doing much chattering through this blog recently and observe with some wry amusement that much of the material for this blog was accumulated back in 2011 – meaning that many of the web references I found back then are long since gone. Oh, how ephemeral this Internet stuff can be!


Cement or Putty?

My first task is to explain why this blog is about Leaded Light Cement and why I do not call it Putty. Using the right word is important because words have meanings.

The words “putty” and “cement” are not interchangeable because there’s a real difference in what they mean, what they are, how they behave and how they are used. Put simply, we use a putty to hold glass in a wooden window frame but we use a cement to waterproof and bond glass into a leaded light window panel.

As the Wikipedia entry for Putty explains, putty is a generic term that describes highly plastic materials, similar in texture to clay or dough, typically used in domestic construction and repairs as a sealant or filler. Notice the words “sealant and filler” do not imply any sense of binding or adherence.

By contrast Wikipedia’s entry for Cement describes a substance that sets and hardens and adheres to other materials so that it can bind them together.

Leaded light cement is therefore a product that we expect to bind to the glass and lead work and we can also expect it to harden as part of a setting process. By contrast putty does neither. This subtle difference explains why “putty” and “cement” are not interchangeable terms even though you’ll soon realise they both have a formulations substantially based on whiting and linseed oil in our sphere of interest.

As I’ve just mentioned, putty and leaded light cement both contain whiting and linseed oil but that’s as far as the similarity runs. So, it’s the additional materials you will find leaded light cement that changes it from being a putty, causing it become a cement. You will learn more about these differences as you wade through my seemingly endless chattering.

Later you will begin to understand why materials such as Plaster of Paris and Portland Cement should never be part of any formulation for putty or leaded light cement.


What Is Glazing Putty?

Although this chatter should be about leaded light cement, it does no harm to briefly mention glazing putty if only to understand more about how it simultaneously has similarities and yet differs from leaded light cement. I’ve already given you some outline hints. But as usual I have more chatter to complete the picture.

Traditional glazing putty, also known as Common Putty, is whiting and linseed oil mixed in a proportion that forms a firm dough that is neither too hard nor too runny to glaze windows. This is just one kind of putty described at Wikipedia. Later in this blog I will look more closely at Whiting and at Linseed Oil as ingredients.

Although I have occasionally encountered comments suggesting leaded lights can be waterproofed with glazing putty, a common complaint is that it is not blackened and that it is the wrong consistency to force under the leaves of lead cames.

A further problem can be seen when comparing old windows in-situ. Leaded light cement deteriorates far more slowly than glazing putty. Leaded light cement is expected to last a hundred years whereas glazing putty will typically last tens of years.

In summary it’s clear that you shouldn’t be using ordinary glazing putty to waterproof a leaded light panel.

With a clear idea of what common glazing putty is, let’s have a look at some leaded light cement recipes. To start with I will generalise. Then we will look at published recipes. We will discover there are many variations on the same theme, some good, some bad and some to be avoided.


Leaded Light Cement – Generalisations

There are numerous recipes for leaded light cement, both proprietary and published, but the core common ingredients are always the same – linseed oil and whiting – so a similarity with traditional glazing putty is not in dispute. However, beyond these two core ingredients are other materials that make it more suitable for waterproofing and strengthening leaded lights. Principle amongst the additional materials are a volatile drying agent and a blackening colourant – more about these additions below.

The consistency of leaded light cement is a matter of personal preference, but should be firm enough that it can be forced under the leaves of lead cames without running through to the back. So, although leaded light cement could be as stiff as Plasticine or Play-Doh, which tends more towards the consistency of glazing putty, it has a more useful consistency when it is less firm than traditional glazing putty, variously described as peanut butter, porridge, a very thick pancake batter which slowly oozes off your hand, treacle or like molasses on a cold morning.

Some published formulations use only boiled linseed oil and others only raw linseed oil. There are others that use half boiled linseed oil and half raw linseed oil. Decisions about which to use or in what proportion relates to their drying properties, more about which I will chatter about later. For the moment, just remember that raw linseed oil takes a longer to dry and stiffen up in leaded light cement than boiled (or refined) linseed oil. These two oils are known as “drying oils” and the word “drying” isn’t in the sense that we’d normally consider to be “drying”. It is very much an “industrial” meaning for the word which actually relates to a hardening process that is the result of chemical oxidation.

Turpentine was traditionally used as a “volatile drying agent” but it is now an expensive product for which turpentine substitute is a more cost-effective alternative. A more modern synthetic alternative that is equally effective but not as pungent as turpentine is spirit white, also known as mineral spirit. Again the word “drying” isn’t quite what we mean in ordinary conversation. The word “volatile” hints that we’re dealing with a substance that evaporates quickly.

The reason for also using a “volatile” drying agent (such as turpentine) in leaded light cement to evaporate quickly from the cement causing it to thicken more quickly than would normally occur with just linseed oil. It therefore accelerates the drying process. This is why leaded light cement hardens within a day or so but common putty (which has no turpentine or equivalent) takes many days to harden.

The primary reason for adding extra liquid drying agents to the cement is to thin the cement to less-firm consistency, so that the cement can be brushed more easily under leaves of lead cames. A less desirable consequence of too much of the liquid components is that it can mean the cement runs out of the back of the panel being waterproofed and remains soft for several days unless measures are taken to assist the drying and stiffening process. The volatility of turpentine, or one of its alternatives, will always results in a faster drying time when compared with an equally runny formulation that uses only linseed oils (whether raw, boiled or in combination).

Although the use of volatile drying agents, such as white spirit, will aid rapid drying, the proportion used should not overwhelm or replace the linseed oil component because it is the long-term polymerisation of the linseed oil that is important to the end result. It is a matter of conjecture that the use of too much volatile drying agent may cause shrinkage or increase porosity of the cement in a leaded light panel.

Leaded light cement typically contains a black colourant which traditionally would be lampblack (black carbon powder, soot) but modern alternatives that are equally effective are “Universal colorants” (powder or liquid), concrete colouring powders, oil-based paints, powdered poster paint or stove blackening compounds. The resulting cement is a medium grey colour that approximates the colour of weathered lead. Be aware that the use of water-based pigments (such as ready-mixed poster paint, acrylic colours or latex) will cause problems because linseed oil and water don’t mix easily.

Some leaded light cement formulations contain small amounts of lead and lead compounds such as white lead, red lead, or litharge. Although no clear references have be found to explain why these lead compounds are sometimes used in leaded light cement formulations, it is reasonable to admit three plausible reasons, any or all of which may have explain their historic use:

  • Lead compounds in the cement may impede deterioration by biological agents (such as fungal or microbial attack) due to lead toxicity. Comparing the longevity of leaded light cement in comparison with typical traditional window glazing putty supports this possibility.
  • The inclusion of lead compounds may lend to the cement a colour and general appearance more reminiscent of lead came than the use of a black colourant alone. It is plausible to suggest that the long-term oxidation of lead compound inclusions in the cement will mirror long-term oxidation of the lead came of a leaded light.
  • The lead salts might be used as a “metal drier” or an anti-oxidant. The use of red lead has been noted as a “hardener” in a recipe from the start of the 20th century and white lead has been used in the past in paints.

In addition to first noting that all lead compounds are toxic, outline notes about common lead compounds is perhaps useful, if only for future reference:

  • White lead has the chemical formula (PbCO3)2Pb(OH)2 and is the pigment used in old paints and old cosmetics. It is now largely banned due to the lead poisoning it causes.
  • Red lead has the chemical name lead tetroxide and has the chemical formula Pb3O4 (or more strictly 2PbO·PbO2) and may become yellow lead following exposure to damp air over time (as the monohydrate).
  • Litharge is the red form of lead(II) oxide which has the chemical formula PbO. The other form of lead (II) oxide is yellow and is called massicot.
  • Lead acetates also exist, and may be produced as a white bloom on new lead cames after a leaded light has been installed using modern synthetic grouts that emit acetic acid vapours when they cure.

With a foundation understanding of the main constituents found in leaded light cement under your belt, it’s now time to consider a few of the many published formulations for leaded light cement.

Some of the recipes below are eminently suitable whilst others contain questionable materials such as Plaster of Paris or Portland Cement. After each recipe I will add some comments to give you a deeper understanding of what I think is good and bad about each one of them. You, of course, are entitled to do your own research, come to different conclusions and disagree entirely with my opinions.


Recipe 1

This is a simplified traditional style formulation. It is the essence of what I read at Ehow.


  • Measure boiled and raw linseed oil in equal parts (for example, 1/2 cup of each) into a bucket.
  • Mix in whiting a cup at a time with a spoon. If you used 1/2 cup each of boiled and raw linseed oil, use up to about four cups of whiting, depending on the desired consistency.
  • Mix in about 1 tbsp of stove or lamp black, depending on how dark you want the cement.
  • Mix everything together until there are no streaks. Use your gloved hands when it gets difficult to mix with the spoon.


The use of boiled linseed oil suggests an intention to increase the drying time of this formulation. However the lack of a volatile drying agent (such as turpentine or white spirits) means this will not have a particularly fast drying time which may cause disappointment. This recipe is substantially the same formulation as Recipe 2 and it is likely that one is a re-statement of the other.


Recipe 2

This is another simplified traditional style formulation. It is the essence of what I read here.


  • 1/2 cup boiled linseed oil
  • 1/2 cup raw linseed oil
  • 4 cups whiting
  • Stove black or black colouring for cement
  • A container for mixing the [not] putty and rubber gloves or nitrile gloves.


Keep adding whiting to the linseed oil mixture, a cup or so at a time to begin with then smaller increments towards the end. Mix using a spoon with gloved hands, much like making bread dough, until lumps are gone and the mixture is smooth.

If you want your black cement, add the black colouring at the end. If you do not use black, the cement will be a light beige colour like traditional glazing putty.


The use of boiled linseed oil suggests an intention to increase the drying time of this formulation. However the lack of a volatile drying agent (such as turpentine or white spirits) means this will not have a particularly fast drying time which may cause disappointment. This recipe is substantially the same formulation as Recipe 1 and it is likely that one is a re-statement of the other.


Recipe 3

This is a faster drying traditional formulation. It comes from a blog.


  • 7 parts by volume whiting
  • 1 part by volume boiled linseed oil
  • 1 part by volume white spirits (turpentine or substitute or mineral spirits)
  • 1-2 Tablespoons lamp black or other colorant


Add the whiting (reserving about one quarter) to the linseed oil and white spirit. Mix this well, by hand or with a domestic mixer capable of mixing bread dough. When these are mixed thoroughly, check the consistency is barely fluid. At this point, add the colorant then add more whiting as required to get the consistency you want.

The author of this recipe says you should make only what you will be using on the current project, as the whiting separates from the linseed oil and spirit relatively quickly, and that since making your own is cheap and quick to make, there is no saving in making a lot.

The author of the recipe also says that commercial cements have emulsifiers to keep the whiting from settling and so extend the life of the product. More about this later!


Recipe 3 reveals a different (higher) proportion of whiting to drying agents than the previous recipes. The higher whiting proportion probably addresses the consequence of using a less viscous mixture of boiled linseed oil with volatile white spirit. The consequence of both boiled linseed oil and white spirit will be a faster setting than the first two recipes. This is a good starting point for your own experiments.


Recipe 4

This fast-setting recipe came from here but disappeared off the Web. It has been found again as the first of two recipes here. The author originally said “This putty sets up faster than commercial putty” which I take to mean it hardens more quickly than commercial leaded light cement.

Dry Ingredients:

  • 4 parts whiting(chalk, calcium carbonate)
  • 2 parts plaster of Paris
  • 1 1/2 parts Portland cement
  • 1/4  part lamp black

Wet ingredients:

  • 1 part – boiled linseed oil
  • 1 1/2 – 2 parts pure gum turpentine


The method implied is that dry and wet ingredients can be stored and then mixed to a desired consistency when required. This is a good idea, but the formulation isn’t.


Recipe 4 is curious for several reasons. It is also bad for several reasons. Use it at your peril.

Specifying pure gum turpentine is needlessly prescriptive because it is expensive and will perform no better than ordinary turpentine or white spirits.

The use of Plaster of Paris and Portland Cement is not recommended, despite this formulation despite the claim it has a much faster setting time. The problem is that plaster of Paris and the Portland cement deteriorate in a damp atmosphere in the long term. A further problem with these materials is that they contribute to an excessively stiff cement which in turn raises the possibility of glass breakage. Another reason not to use Portland cement is that it strongly attaches itself to glass making future restoration activities more difficult. And in relation to your health and safety a problem is that Portland Cement becomes strongly caustic and can cause skin burns as well as severe eye or respiratory irritation. Health and safety problems also arise with the used of plaster of Paris.


Recipe 5

This is another fast setting recipe and is the second of two recipes found here.

Dry Ingredients:

  • 1 part calcium carbonate (whiting/chalk)
  • 1 part plaster of Paris
  • 1/4 part lamp Black

Wet Ingredients:

  • 1 part boiled linseed oil
  • 1 part – white spirit (paint thinner)


Recipe 5 is an improvement over recipe 4 but is still not recommended. One improvement is that less-expensive white spirits are now used. Another improvement is that Portland cement is no longer being used. The problem is with the Plaster of Paris.

The wet ingredients hint at a fast drying time and although the use of Plaster of Paris may be less hazardous than Portland cement, it is still not appropriate for reasons outlines in the previous recipe. Use this recipe at your peril.


Recipe 6

This recipe came from a book called Decorative Glass by Nance Fyson (page 164) and is interesting because it starts with traditional glazing putty and turns it into leaded light cement.


75% linseed oil putty – traditional glazing putty
10% white spirit and 5% linseed oil mixed
10% lampblack
Whiting as required


Place in a bucket. The white spirit and linseed oil mixture is added to the  lampblack then putty is added, a little at a time. To adjust consistency, more white spirit to thin or whiting to thicken. To darken add more lamp black.


Recipe 6 is a practical and convenient suggestion in that the formulation starts with inexpensive traditional glazing putty and adds other materials to formulate a sound and sensible leaded light cement.

The use of white spirit is cost-effective and the extra linseed oil could be boiled linseed oil would improve the drying time. The addition of the white spirit and linseed oil will soften the mixture to make it more suitable as a leaded light cement – and the exact amounts can be varied to achieve the desired consistency.

Though not stated in the original recipe, using black powder paint (or some other suitable oil-based blackening agent) in place of lampblack would make the recipe more easily accessible to any modern stained glass craft worker who doesn’t have a ready supply of lampblack or soot.

This recipe is recommended if you want a quick, convenient and economical method of making your own leaded light cement, particularly if you have some left over glazing putty and have easy access to the other ingredients.


Recipe 7

This recipe was found at Project Gutenberg in a book called  Stained Glass Work – a text-book for students and workers in glass, by C. W. Whall. When you’ve downloaded it, search for “How to Cement a Leaded Light“.


Whitening, 2/3 to plaster of Paris 1/3; add a mixture of equal quantities of boiled linseed-oil and spirit of turpentine to make a paste about as thick as treacle. Add a little red lead to help to harden it, some patent dryer to cause it to dry, and lamp-black to colour.


This recipe comes from the start of the 20th century so it’s old. It is interesting in that it does lend some credence to the traditional (though not necessarily common nor sensible) use of Plaster of Paris in leaded light cement. It resembles recipe 5 in that they both use Plaster of Paris.

The use of red lead is confirmed as a “metal drying agent” but is not a practical proposition for most stained glass workers given the toxic nature of lead compounds and widespread legislative restrictions on their use. However, the mention of lead compounds does link nicely to some modern leaded light cement formulations that mention lead as one of their ingredients.

The reference to a ‘patent drier’ is an unhelpfully vague reference perhaps to a catalytic drying agent (that accelerates the oxidative polymerisation of the linseed oil) rather than to a volatile drying agent such as turpentine (that simply evaporates quickly).

This is an old recipe that isn’t recommended, mainly because it uses Plaster of Paris and red lead.


Commercial Formulations

Seeking out manufacturer’s safety data sheets (MSDS) and looking closely of packaging labels sometimes provide us with useful hints about  the formulation of their products. From such sources we get some hints about modern commercial leaded light cement products.

Here we learn that their “putty” is a dough-like compound of whiting and linseed oil which may contain small amounts of white lead, red lead, lampblack and/or litharge (which is lead(ii) oxide). Those lead compounds are probably intended as metal drying agents.

And here we discover a formulation that contains naptha, orange lead, mineral filler, linseed oil, a plasticiser and white spirit. The term “mineral filler” we can assume to mean “whiting”. Notice we find linseed oil and white spirit in this recipe. Notice also that there is orange lead as a metal drying agent but no mention of lampblack or carbon black.

As a simple confirmation, this web page suggests that commercial glazing putty is exactly what we’d expect – nothing more than a ” Homogeneous mixture of mineral filler and linseed oil” for which we again assume that “mineral filler” actually means “whiting”.

Arbo leaded light cement used to be described here but the web page has now disappeared. It used to say that their leaded light cement contained a vegetable oil, mineral fillers, white spirit and metal driers. For the term “vegetable oil” we can assume “linseed oil”, for “mineral fillers” we can assume “whiting” and for “metal driers” we can assume a special metal drying agent. This metal drying agent will be chosen to catalyse (ie accelerate) the drying process by a process of oxidative polymerisation of the linseed oil (which makes the linseed oil thicken and harden) and may or may not be a lead compound of the kind seen in other formulations.

Comments here suggest there may be commercial formulations of “putty made for stained glass” that contain Portland cement and/or Plaster of Paris. The comments are, I assume, meant to offer us advice relating to commercial formulations of “leaded light cement” rather than “leaded light putty”:

If you are using a commercial putty made for stained glass, look for one that does not contain cement or plaster of paris. A good indicator of what not to buy is if the product contains the word cement in the name or description.

Although the author of that web page is correct to suggest that [Portland] cement and Plaster of Paris are a bad idea, the remaining comments are of dubious value because of the confused use of “putty” and “cement”. Think about it – the recommendation is not to purchase a properly formulated leaded light cement because there’s the word cement in the name – this is patent nonsense.

Although the web page here is now long gone, the forum thread had a similar comment about commercial “putty” (as usual, actually meaning leaded light cement):

Everyone has their personal favourite formula or brand. If you elect to buy premade putty [meaning leaded light cement], take care to read the list of ingredients. Reject ANYTHING that contains plaster or cement. Both are NOT waterproof but will absorb moisture and generate mold and mildew.

This time the author correctly limits product rejection to just those with ingredients that contain the words plaster or cement rather than in the name of the product. The comment about the water absorbing nature of Plaster of Paris and of Portland Cement is both useful and correct and will be described in more detail later. Again the key message is not to use leaded light cement with Plaster of Paris or Portland Cement as ingredients.

The web page here from which Recipe 3 was taken, says that “commercial cements have emulsifiers to keep the whiting from settling and so extend the life of the product”. I have found no evidence from any MSDS documents to support this claim. I also think it is unlikely to be correct because two immiscible liquids are required to form an emulsion and although we have oil-based liquids we don’t have water-based liquids in leaded light cement.

Another commercial stained glass cement formulation is a two-part American product called Miracle Mudd. You will find related MSDS documents here for the dry component and here for the liquid component.

Information gathered from the MSDS documents is typically sparse. This is not unusual because they don’t want you to know what you’re paying for, especially not when it’s “nothing special”.

The MSDS document for the dry part tells us it’s a grey powder that’s not reactive and not appear to be particularly hazardous to our health. If there were Plaster of Paris or Portland Cement involved I would expect the health hazard data and control measures to be greater than described. I would therefore speculate that it’s a mixture of whiting and some kind of colourant powder such as poster paint, brick colourant or perhaps even lampblack. So, nothing special here so far as I can tell.

The MSDS document for the liquid part tells us that it is an “amber to dark brown oily liquid with a pine aroma” with a boiling point of 307°F and flash point of 105°F. Also, an advertising claim is that it isn’t so smelly as competing products. Pulling these facts together is suggestive of the liquid part having a formulation that involves turpentine and linseed oil or derivatives of them. So, nothing special here so far as I can tell.

In conclusion, my guess is that Miracle Mudd is a traditional leaded light cement that you happen to purchase as separate dry and liquid parts and mix yourself. In this respect it is reminiscent of recipes 4 and 5 but probably without the nasty Plaster of Paris or Portland Cement. So, the miracle of Miracle Mudd would appear to be that it comes in two parts which doesn’t really seem to be such a great miracle.

Before I completely bore you to tears I think it’s time to stop looking at commercial formulations and pull together some general comments about the formulation of leaded light cement.


General Formulation Comments

A potentially good idea hinted-at by the authors of recipes 3 and 4, as for Miracle Mudd, is that dry and wet ingredients can be prepared and stored separately. This allows you to only make-up the amount of leaded light cement that you intend to use which in turn should reduce the amount of waste.

If you are making your own leaded light cement try to make only what will be needed for the current project. If you purchase ready-made leaded light cement try to buy quantities that are not excessively large. The problem with leaded light cement is that the whiting slowly separates from the oily liquid portion, resulting in a solid mass hiding under an oily surface. This separation is not permanent and can be reversed– loosening the solid portion, breaking it down and re-mixing it back into the oily portion with something like a palette knife or wallpaper scraper works but it takes a lot of time and patience.

Since making your own leaded light cement is quick and cheap, there is no saving in making large amounts in a single batch. If necessary, as hinted-at by some recipes, make-up and store dry ingredients and wet ingredients in distinct containers. Or consider the recipe from the book which adds ingredients to ordinary glazing putty.

One commentator suggests that a batch of leaded light cement has a shelf life of just one day but does not say why this should be so or the conditions that cause this to be the case. It is however plausible that formulations containing Plaster of Paris or Portland Cement may chemically ‘go off’ in consequence of the effects of atmospheric water moisture. If you’re sensible and are not using Plaster of Paris or Portland Cement then this should never be a problem.

Whether you are using a commercial glazing putty or a commercial leaded light cement, look for one that does not contain Portland Cement or Plaster of Paris. Although none of the MSDS documents I examined suggested that commercial formulations contain them, it does not mean that none of them do.

If your cement mixture is too stiff add just  a little more white spirit to get it to your desired consistency. Conversely, if the mixture is too soft or runny add more whiting to stiffen the mixture.

If you are making a big batch of leaded light cement the mixing task can get physically difficult. In such circumstances using a bucket and an electric drill-powered paint stirrer becomes preferable to using a kitchen blender, kitchen mixer or a spoon.

And that’s all the advice I can give other than to suggest you experiment, do your own research and come to your own conclusions. I am not the fount of all knowledge!

For the remainder of this blog I’ll change the focus to an examination of the various component materials. Expect some repetition but I hope there’s not too much for you to bear.


What Is Whiting?

Whiting forms the bulk of the leaded light cement used to waterproof leaded lights in much the same way as whiting forms the bulk of glazing putty used for a traditionally glazed window.

Whiting is also used as a desiccant or drying agent to remove excess oils from leaded light cement during the “cleaning-up” process, thus promoting a faster setting time. Whiting serves as a mild abrasive to help remove excess cement and to polish the glass and leading as part of the final cleaning process.

Whiting is an archaic name for finely powdered white chalk. It has the chemical name calcium carbonate and the chemical formula CaCO3. However, not all “chalk” you’ll find being sold is calcium carbonate.  So, be careful when purchasing “chalk” because it can also refer to other compounds including magnesium silicate and calcium sulphate. Although traditionally composed of natural chalk, modern blackboard chalk is generally made from the mineral gypsum (calcium sulphate).

Chalk is used to marking lines on playing fields and although some of these products are still made with calcium carbonate, it is titanium dioxide that is often used nowadays. Sports such as gymnastics, rock-climbing, weight-lifting and tug-of-war also make use of chalk though nowadays it is usually magnesium carbonate.

Whiting should not contain any calcium oxide (quick lime) or calcium hydroxide (slaked lime or hydrated lime). Calcium carbonate is a neutral substance that can be handled easily and safely but calcium oxide and calcium hydroxide are caustic alkaline substances that can be hazardous.

The building trade also use line marking chalk which may (or may not) be calcium carbonate. Painting and DIY outlets may have calcium carbonate (in stock or to order) where it will probably be sold as whiting or chalk dust. Pottery supplies stores may sell calcium carbonate where it will probably be called calcium carbonate or chalk dust.

Agricultural or feedstuffs merchant and garden centres may have whiting but be sure it is calcium carbonate (chalk) and not calcium oxide (quick lime) or calcium hydroxide (slaked lime) or some non-specific formulation such as “field lime” that may contain calcium oxide or calcium hydroxide. Also be wary of “field lime” because it can be very gritty and scratch your glass.

Lime plaster is a mixture of calcium hydroxide, sand and other fillers. The calcium hydroxide reacts exothermically with water and ultimately forms calcium carbonate. Whitewash is the same chemistry. As both involve calcium hydroxide they should be avoided in stained glass crafts. Despite this, some workers use lime, Plaster of Paris and related materials in their stained glass cement to achieve a faster setting time even though such formulations are more hazardous and less suitable than those that use whiting.

So, perhaps the best place to buy whiting for stained glass crafts is from a reputable stained glass store where the purpose for its use is well understood.


What about Plaster of Paris?

Plaster of Paris is also known as Gypsum Plaster because is produced by heating a type of rock called Gypsum. Plaster of Paris is more properly known as calcium sulphate semi-hydrate, with the chemical formula CaSO4·0.5H2O which tells you it contains just a little water. Adding water to Plaster of Paris turns it back to Gypsum, which has the chemical formula CaSO4·2H2O which means it now contains more water. So, in essence, Plaster of Paris relies on water to turn it back to “rock hard” gypsum.

Therefore the first and obvious question to ask is how it could be possible that Plaster of Paris might be a suitable component for leaded light cement when all the other ingredients (linseed oils and the drying agents such as white spirits) do not contain water. The chemistry of Plaster of Paris tells us that water that is needed to make it harden but the only source of water we have available must be rain and damp air. Something is not right here – we can not expect Plaster of Paris to contribute to waterproofing a leaded light panel if it needs water to make it harden. The only way the Plaster of Paris can “work” in leaded light cement is if it “compromises” the ability of the cement to repel water and moisture.

Another less obvious problem with Plaster of Paris is that it hardens to a hard and very inflexible state which is not desirable in a well-formulated leaded light cement. In well-formulated leaded light cement the resulting matrix of whiting in polymerised linseed oil is waterproof and strong but not so rigid as solidified Plaster of Paris. So, leaded light cement containing Plaster of Paris is more likely to crack the glass in leaded lights because it is too rigid. This is reflected in comments here where it says that “recipes that use plaster of Paris or [Portland] cement are not recommended because the product is too hard and stiff when dry, providing no cushioning for the glass inside the lead frame. A slight rubberiness is desirable to provide support without the stiff restraint of the cement, which can cause the glass to break.”

In summary, Plaster of Paris should never be a component in your leaded light cement.


What about Portland Cement?

Portland cement is a “hydraulic cement” meaning it hardens when exposed to water, becoming water-resistant (rather than waterproof). It is what you use to make concrete.

Quicklime, or calcium oxide, CaO, is a major component of Portland Cement and as such its nasty stuff. This makes Portland Cement highly alkaline which means it is strongly caustic and will cause skin burns if not promptly washed off with water. Similarly, dry cement powder in contact with mucous membrane can cause severe eye or respiratory irritation.

Everything that you just read about the use of Plaster of Paris also applies to Portland Cement.

In summary, Portland cement should not be a component in your leaded light cement.


What is Linseed Oil?

Linseed oil is a major component of both glazing putty and leaded light cement and is also known as flax seed oil. You can read lots about it at Wikipedia.

Linseed oil is what is known as a “drying oil”, which means it polymerises over a period of time (days or weeks) to form a solid mass. This polymerisation causes glazing putty and leaded light cement to harden to a rigid (rather than brittle) state over the course of several days. As a triglyceride, the water-repellent (hydrophobic) nature of linseed oil is also an advantage for its water-repellent weatherproofing properties. Read more about “drying oils” here if you have the enthusiasm because it’s the key to how leaded light cement achieves what we’re after – water-repellent strength without excessive rigidity.

Linseed oil is available either as raw linseed oil or boiled linseed oil. Boiling linseed oil causes it to partially polymerise and oxidise, making it thicker which in turn means it has a shorter drying time. Most products labelled as “boiled linseed oil” are now a combination of raw linseed oil, a volatile petroleum-based solvent (which evaporates quickly) and metallic dryers (which are chemical catalysts that accelerate drying).

As noted at the long-gone Stained Glass Town Square forum, raw and boiled Linseed oils are available (in-stock or to order) from a painting and decorating or DIY outlet. Art suppliers are also a source but are usually more expensive. Some agricultural or animal feed merchants might sell raw linseed oil as a feed supplement for horses.


What About Volatile Drying Agents?

Leaded light cement formulations often include turpentine, turpentine substitute or white spirits. There is little (if any) practical difference between these different products when used as a volatile drying agent in leaded light cement, the significant differences being how they smell and how much they cost.

Turpentine is a natural product derived from pine trees. As a natural product it tends to be expensive, particularly when highly purified.

Turpentine substitute (mineral turpentine) is an inexpensive petroleum-based replacement for turpentine. It consists of a complex mixture of highly refined hydrocarbon distillates mainly in the C9-C16 range, typically containing at least 60% white spirit and 20-40% naptha (petroleum). Low odour turpentine is close to 100% white spirit.

White spirits are the inexpensive petroleum-based replacement for turpentine, consisting of a complex mixture of highly refined hydrocarbon distillates. So, in addition to being cheaper, white spirits are less flammable and less toxic than turpentine and turpentine substitute.

Therefore, it seems, any of turpentine, turpentine substitute or white spirit will suffice but white spirit causes less smell and is the cheapest.

Paint thinners are a solvent commonly held to mean white spirits, turpentine or turpentine substitute. It can also be taken to include other solvents such as acetone, xylene and toluene. So, be aware that when you want to clean your glazing brushes paint thinners may not always mean white spirits.


What about Colourants?

Traditional glazing putty is a pale brown colour but leaded light cement tends to be shades of grey tending towards black. The colour was traditionally introduced by the use of lampblack which is nothing more than soot, which in turn is just powdered carbon.

Comments from the long-gone Stained Glass Town Square forum suggest that leaded light cement can be colored with stove blackening products (such as tubes of Zebo or Zebrite), concrete colouring (powder), powdered poster paint, oil paint and the traditional lamp black (powder).

This forum thread also warned against the use of any water-based pigment because they cause problems with linseed oil putty (because water doesn’t mix well with oils!). This also means that latex and acrylic colours are not acceptable.


What about Other Additives?
Lead and lead oxides were used in traditional formulations for leaded light cement but due to the toxicity of lead compounds their use is less common in modern formulations.

Why lead and lead oxides were used is not clear but one rational possibility for using them might be that they are toxic to all kinds of life including algae, moss and lichens that might attempt to establish themselves on your leaded light. Of these lichens would perhaps be the most difficult to avoid as they are well-known for their ability to tolerate concentrations of heavy metals, such as lead, that kill other forms of plant life.

Another possible reason for using lead compounds in leaded light cement relates to their possible use as a drying agent. In this context they may be catalysing the oxidative polymerisation of the linseed oil – making the linseed oil harden more quickly.

Unless you have a particularly strong justification for using lead or lead oxides in your own formulations for leaded light cement I recommend that you stay clear of lead compounds in the interests of your health.

If you have the enthusiasm for a brain-stretching read, have a closer look at Oil Drying Agents at Wikipedia to understand more about how some additives help to accelerate the drying of oils.


Cheaper Oils and Solvents

Boiled linseed oil is cheaper and ‘cures’ faster than raw linseed oil. This is why some formulations use a mixture of both. Ultimately they both become the same polymerised material in your leaded light panel .

White spirits are cheaper and just as effective as turpentine substitute which in turn is cheaper and just as effective as pure natural turpentine. Ultimately they all serve the same purpose and will all evaporate out of your leaded light panel.


That’s All Folks!

Thank you for your patience reading this blog. I hope my chatterings have been useful. Do try some experiments of your own and let us all know how successful they were.


Posted in leaded light, Leaded light cement, Putty, Whiting | Tagged , , | 10 Comments

Make Your Own Glass Cleaner

Today I want to chatter about glass cleaning products that are used on kiln-fired glass, discovering who’s using what and talking about what works and why, and then talk about how you can make or choose the best glass cleaner.

If you’re hoping to read about ordinary household window cleaning products then this blog is unlikely to be of interest, although I will make some passing comments that you may find helpful.

The Motivations

A key motivation is to ask why we pay for a brand name when a generic product or home-made product does the same job, sometimes better, and is cheaper? You might suppose that there’s something special in the branded product but often you’ll discover it’s nothing more than an uninspired formulation of standard raw materials.

Another motivation is to consider why we use glass cleaning product. There are people who use commercial products just as there are others that do not clean their glass before putting it into a kiln. It’s all rather confusing when all you want to do is reduce the incidence of devitrification on you glass masterpiece.

A third motivation is to consider some of the questionable advice found on the Internet when one cleaning product is often recommended in preference for another but without clear reasoning or justification.

Why Bother Cleaning Glass?

The boiled-down essence of “perceived wisdom” is that we need to do whatever is necessary to reduce the number of nucleation sites on the surface of our fusing glass which could lead to devitrification. Basically, it’s any kind of “muck” on the surfaces of your glass that form these nucleation sites that can provoke the devitrification process. The process of devitrification is the result of normally amorphous crystalline glass changing progressively into regular crystalline glass. If you are a keen and enthusiastic learner have a look here to understand more about crystal formation, paying particular attention to the section about “heterogenous nucleation”.

The reason that some people get obsessive about cleaning glass before use is that they believe even the merest hint of a fingerprint or dust on glass will result in devitrification. Others suspect it’s perhaps just a big conspiracy theory, believing that any contaminant on glass will simply burn away, just as white PVA glue or Glastac is supposed to do. Think about both sides of the argument because both sides can’t be simultaneously true but both have some truth to them.

The bottom line is that if we really want to clean our glass then something we must hold in our minds is that a glass cleaner should evaporate and not leave any residues whatsoever if it is to leave your glass in a pure unsullied state.

Who’s Using What?

It’s maybe a good idea to start by finding some examples of who is using what to prepare their glass for firing. We can then look at what’s in those products to understand why they work and why they might not be ideal formulations.

Over here in 2010 we find Spartan Glass Cleaner being recommended by someone from Bullseye in response to a mention of a professional glass cleaner from Bohle being used by someone who has a problem. This forum thread is particularly interesting because the advice is well-meant but smacks of “product placement” because Bullseye sell Spartan Glass Cleaner.

Elsewhere I see another “product placement” in the same forum in 2010 where a lack of understanding that “rubbing alcohol” and “denatured alcohol” are not the same thing leads to another “product placement” for Spartan Glass Cleaner, again by someone from Bullseye. Overall, this forum thread gets my vote for whacky advice and mis-information.

But we do now have two named commercial products and two “alcohols” to start the ball rolling for our investigation…

  • Bohle glass cleaner
  • Spartan Glass Cleaner
  • rubbing alcohol
  • denatured alcohol

Let’s look at them in more detail.

If you look for Bohle glass cleaner you find you’ll find that they actually produce more than one product. Find their safety data sheets here and study them, looking for the section in which you find their ingredients. You will find their glass cleaners contain isopropyl alcohol and a surfactant called 2-butoxyethanol. We will individually consider these chemical components later.

We now move on to the aforementioned “Spartan Glass Cleaner” and you will also find that Spartan Chemicals make several glass cleaners. The particular Spartan product that Bullseye sell here seems to be this product from Spartan Chemical and lower down on the same page you’ll find the safety data sheets in three languages, the American language version being here. From the manufacturer’s safety data sheet we learn that Spartan Glass Cleaner contains mostly water, some isopropanol and a little acetic acid. Curiously the safety data sheet for the product suggests a “floral fragrance” which I can only assume means the addition of a small amount of unlisted perfume to mask the acrid smell of acetic acid.

Rubbing alcohol has been mentioned in the forums. It has a strange name because it describes the intended use rather than a specific chemical. So, as you’ll find at Wikipedia’s page for rubbing alcohol it’s likely to be some water with either isopropyl alcohol or ethanol with the possible addition of various additives, some some of which may make it taste bitter and undrinkable and others that have mild medicinal qualities. This lends some credence to a forum contributor here that says rubbing alcohols “sometimes contains impurities, like oils”. Therefore, in summary, rubbing alcohol is an ill-defined product that is mainly made using alcohols that will quickly evaporate but may also contain additions that will not evaporate after cleaning our glass, leaving a small amount of residue. These ill-defined additions are a possible trigger for devitrification if they do not cleanly burn off in a kiln.

Denatured alcohol is also known as methylated spirits and is a mixture of chemicals though typically it is ethanol that dominates, with the addition of some water. It is difficult to pin down precisely what the formulation is because many possible additives are added to the ethanol to make it taste bitter and undrinkable. Whatever the mixture, the alcohols will evaporate completely and quickly because they are volatile, just as they will do for rubbing alcohol. Other additive, such as dyes and bitter-tasting denatonium (as with rubbing alcohol) are a possible trigger for devitrification if they do not cleanly burn off in a kiln.

Domestic Window Cleaning Products

Here I just want to make a few passing comments about what we might call a general purpose window cleaning products. By this I mean something you’d choose to routinely use in a domestic setting.

My first observation is that I don’t really see how Spartan Glass Cleaner can be considered to be special. It certainly does not appear to be specifically designed for our precious fusing glass. More to the point, the formulation appears to be what one might expect from a general purpose window cleaning product (by virtue of the vinegar and having a fragrance) and indeed it seems to be sold by Spartan Chemicals as a general purpose glass and window cleaning concentrate.

A similar observation can be made regarding the Bohle glass cleaners as they too do not appear to be specifically designed for our precious fusing glass.

There is however one very useful comment mentioned here that warns us to avoid extremes of pH (meaning acidity or alkalinity) because they can attack metallic structures such as lead or zinc cames. In other words, glass cleaners that contain ammonia or vinegar at significant concentrations should be avoided. However, because we spray our windows with products that contain only low concentrations of ammonia (or vinegar) then wipe it all away within minutes I fail to understand how any damage can be done to the glass itself and there is little time available to corrode metal work.

Looking More Closely

We have now looked at four products that have been mentioned in forum threads and I’m sure that many others could be added. But let’s press on to the interesting stuff. It’s time to consider the key chemicals from which they are made so that we can better understand what’s good, what’s not and why.

Water is a common ingredient. As we all know, pure water boils at 100 °C and should be neither acidic nor alkaline. Water is probably the most familiar solvent we use and it will not easily cause our glass to devitrify. It is a cheap chemical because it’s so abundant, even if we choose to pay extra for deionised water or even more for distilled water because we don’t have a nice clean soft water supply coming from out taps (American: faucets). The only concern here is the use of hard water because of the dissolved minerals which might come out of solution when cleaning glass because tiny mineral particles can act as nucleation points for devitrification. With regard to distilled vs. deionised water I note that although distilled water is very pure, it should be noted that deionised water has the ionic mineral components removed so is much cheaper to produce and just as usable as distilled water for cleaning glass. Sometimes spending that extra money doesn’t really give you any significant advantage.

Isopropyl alcohol has many chemical synonyms such as isopropanol, propanol and propan-1-ol. We’ve already seen isopropyl alcohol mentioned in the safety data sheets for both of the commercial products as well as for the rubbing alcohol (and possibly for denatured alcohol). So is important we know more about this particular alcohol. In essence, isopropyl alcohol is a pure chemical, not a commercial formulation, which means we can know exactly how it behaves. It is volatile with a boiling point of 82.6 °C which means it evaporates quickly and completely. It is neither an acid nor an alkali so it will not attack glass. It is an effective solvent in many situations and is also cheap to manufacture so you will find it being used in many diverse cleaning products. These are all good characteristics for a glass cleaner, explaining why each of our four example products involve isopropyl alcohol.

2-butoxyethanol has many synonyms of which 2-butoxyethan-1-ol is its favoured chemical name. In essence it’s another pure chemical, not a commercial formulation, which means we can know exactly how it behaves. It is a non-volatile solvent of low toxicity that has mild surfactant properties and has a mild sweet smell. In other words, it’s a gentle cleaning agent that doesn’t evaporate quickly so is useful for cleaning mucky glass. It has a boiling point of 171 °C which means that any of it that is not cleaned off our glass ought to evaporate completely in a kiln. Surfactants are something we’re more familiar with in washing-up liquid and other “harsher” household washing and cleaning products and the reason they’re often used is because they’re good at “lifting dirt”.

Acetic acid is also known as ethanoic acid and when diluted we know it as vinegar. When in Britain, be sure to add some to your fish and chips (American: fries) if it’s of the malted vinegar variety. Acetic acid has a boiling point of 116 °C which means it should evaporate completely but not very quickly but we must remember that acetic acid is mixed with plenty of water to form what we know as vinegar. Vinegar has been used to clean things for time immemorial and is used in some glass cleaning formulations such as Spartan Glass Cleaner as promoted by Bullseye as well as domestic products such as Windowlene in the UK. It is a cheap and abundant chemical. It is a weak acid being used in small quantities, and because we don’t spend hours cleaning a piece of glass, it is unlikely to cause any problems for our fusing glass surfaces.

Though not mentioned in the four products we’ve been looking into, it would be remiss of me to ignore ammonia which is a synonym for household ammonia and ammonium hydroxide. It does happen to be used in a Spartan glass cleaner promoted as being “fortified with ammonia” and you’ll find the MSDS here. But I digress. Ammonia is volatile and has a boiling point of around 27 °C and is a commonly used in small quantities, diluted in water, as a solvent in some household window cleaning products. Only because ammonia tends to be used in small quantities within window cleaning products, and because we don’t spend hours cleaning a piece of glass, can we assume the ammonia it is unlikely to cause any problems with our fusing glass. It just smells absolutely horrible.

We can not identify the un-named but implied fragrance perfume in Spartan Glass Cleaner and can only assume that if it’s not causing Bullseye any problems. We can however guess that it’s probably some kind of organic molecule (or mixture) that successfully burns off in a kiln. But, if we are worried about devitrification and want to avoid contaminating the glass then shouldn’t we also want to avoid things like fragrance chemicals that aren’t needed to clean our glass? This is an interesting concept to consider! All I can suggest is that the only logical reason to add a perfume to a cleaning product is to mask the smell of something unpleasant – like vinegar or ammonia.

And finally, I have one more chemical that deserves a mention because it’s rarely mentioned. It’s called acetone and is also known as propanone. Add some colour and perhaps some fragrance and we call it nail polish remover. Acetone is very volatile and has a boiling point of 100 °C which means it will quickly evaporate and leave no residues. It is neither acidic or alkaline so will not attack glass. The colorants and perfumes added to nail polish remover make it impure and therefore less desirable than pure acetone. The only link on the Internet I can recommend reading that knowledgeably relates to the use of acetone to clean glass is here.

Looking Wider

Having discovered and learned a little about chemicals that are commonly used, it’s time to trawl the Internet for more examples of what people are using to clean their glass. The best source I encountered comes from a long forum thread here at Fused Glass in 2008 that reveals many examples of what people do to clean their glass.

What follows in this section is a brief summary of what caught my eye in that forum thread and I don’t suppose attitudes and behaviours have changed much in the succeeding decade.

One person uses distilled water and vinegar, commenting that they use distilled water due to having a hard water supply. Avoiding hard water is a good idea because of the dissolved mineral that might come out of solution, leaving scummy particles that might just provoke the nucleation which cause devitrification. Again we see readily available vinegar being used. What is not clear is whether the water and vinegar are separate cleaning steps or whether they are mixed together. I personally would hope this person used the vinegar as a first step then rinsed using the distilled water.

Another person uses hot water with a small amount of soap. This sounds reasonable because the soap and water will be effective with most kinds of contamination. The kind of soap is not mentioned though some (such as washing-up liquid) often contain surfactants (like the 2-butoxyethanol used in the Bohle glass cleaner) whereas others (particularly hand-made soaps) may contain an excess of oils and fats and might therefore leave a thin greasy residue which ought to burn off in the kiln. But for a good cleaning regime it is important to ensure that soap residues are completely removed with a thorough rinse.

Another related comment in the forum thread is the use of warm water with a little dish soap followed by rubbing alcohol. I like this regime better than the previous example because there is a rational two-step regime. Not only does the alcohol rinse away any remaining dish soap but it also serves as a different kind of solvent. The only problem I have with this regime is that it is two steps which implies lots of time and effort.

One contributor reveals what is, in effect, the reverse process, saying ” I use alcohol, then I wash it is very hot water & Dawn dishwashing soap”. Dawn dishwashing soap is what I’d call washing-up liquid, probably a perfumed, mixture of chemicals that includes a surfactant that should be well suited to removing a variety of contaminants. However, this regime would be more reliable and more effective if the alcohol was the second stage, if only to ensure that the washing-up liquid residues are completely removed by the alcohol wash.

And then there’s someone who uses an undefined alcohol and another who uses isopropyl alcohol. As we’ve seen with the Bohle and Spartan glass cleaners, alcohols are widely used because good for cleaning glass.

A curious comment is from someone who says they attended a workshop at Bullseye and they use a mixture of 50% white vinegar and 50% denatured alcohol. This seems to be at odds with what the people from Bullseye have been saying in the forum threads I mentioned at the top of this blog though one might rationally argue that this forum thread is from 2008 whereas the people at Bullseye were recommending Spartan’s products in 2010. But regardless of this observation, the quantity of white vinegar being used seems to be rather excessive, even when we recall that vinegar is acetic acid diluted with lots of water. A small quantity of the white vinegar added to the alcohol would be just as effective and would not smell so horrible. In fact, I’d hazard a guess that omitting the vinegar would be equally effective.

Of course, there are also some people who are using ordinary domestic window cleaning products. But, to be blunt, is that not what the Bullseye recommended Spartan glass cleaner and the Bohle glass cleaner seem to be?

And, for completeness, I should mention that there were some people in the forum thread who’ve been told not to bother cleaning glass because the contaminants will all burn off. This is questionable advice because only the chemicals and contaminants that cleanly burn or evaporate will disappear and not cause a problem. Try burning off particles of grit for example!

 Make Me Laugh

The quote below from the same forum thread at Fused Glass and I find interesting because it reminds us to question what we are told, do our own research and to not assume that a supposed expert is always right, whether the advice is from a face-to-face encounter with a real person or via the Internet.

I took classes from a ” prominent teacher ” who also gave incorrect information….lots of it actually.  Forums such as these are an excellent source of information and have taught me MORE than the prominent teacher.”

If you’re now of the opinion that forums are good and experts are unreliable then consider the advice given here at the Glass Fusing Made Easy web site. It tells us…

Detergents, dish soaps, multi-purpose cleaners, some window cleaners, ammonia and even denatured alcohol should not be used to clean glass.
The Bullseye site suggests that you purchase a cleaner called Spartan Window Cleaner.

Though well-meaning, it’s rather lacking in rigour. Where is the justification and reasoning to support any of this advice? More to the point, there’s a bland assumption that Spartan Window Cleaner must be a good choice because Bullseye recommend what they sell.

Remember folks, I regularly and deliberately tell you to question everything you read on the Internet. I even tell you to not assume I know what I’m talking about. Don’t take my advice without question and likewise don’t take advice from anyone else without question. Think things through and make your own decisions.

My Recommendations

No matter what you decide to use for cleaning glass, if indeed you choose to clean your glass, just make sure the glass is cleaned thoroughly then buffed until it is dry. If you stop buffing when the glass is still wet then the contaminants dissolved in your glass cleaning liquid will be left behind (nicely smeared) on the glass surface when the remaining glass cleaning liquid evaporates.

Use a lint-free cloth if you can for your drying and buffing, but if you can’t then try using good quality paper kitchen towels instead. Cheap paper kitchen towels can leave a residue of paper dust so try not to use such products.

If you find that a piece of glass does not seem to be completely clean after trying to clean it with one kind of cleaning product then repeat using the same cleaning product if it previously made some good progress.

Do remember that you can choose a different cleaning product for your second cleaning attempt, especially if the first cleaning product is having difficulties with the contaminant. Different cleaning products have different capabilities because they contain different solvents.

If you are going to use a cleaning product that contains a soap or surfactant then consider a second rinsing to be sure the soap residue is removed. Be especially aware that some kinds of soap (particularly “super-fatted” hand-made soaps) may leave a thin greasy residue on the glass you just cleaned.

I am an advocate of using pure solvents that are devoid of non-essential additives. I therefore tend to use neat isopropyl alcohol or neat acetone as my cleaning solvents. But remember that I’m not afraid to pre-clean mucky glass with soap and water. Of all the recommendations I give you in this section, this is the paragraph I want you to remember!

Isopropyl alcohol and acetone are volatile and flammable. Take care when you use cleaning products that contain these chemicals. Take care with acetone near plastics as it’s good at melting some of kinds of plastic!

I believe that touching glass with a finger is overstated as a risk for devitrification if your hands are reasonably clean. I have found that white PVA glues are far worse than fingerprints for causing devitrification. So the simple advice here is to try washing your hands before you work with your glass!

And finally, don’t get obsessive about glass cleaning. Just use a quick and effective cleaning regime that works.

Choose Your Cleaning Product

You should now be aware that several different chemicals can be found in glass cleaning products and that you now have an idea of what other people are using. You now also know that there’s nothing particularly special about expensive proprietary commercial glass cleaning products. You also know that water (soft, deionised or distilled), acetone and isopropyl alcohol are the key solvents you need to consider.

Ideally, you will need to find a local supplier of “industrial chemicals” or maybe “industrial solvents” to buy your distilled or deionised water, isopropyl alcohol or acetone, but they should cost you a lot less that buying them from your local stained glass supplier.

An example supplier that I’ve mentioned in the past is APC Pure. I don’t mention them because I work for them or get any commission from them. I simply mention them because they’re local to where I live and they’re an example of the kind of company you should be looking for. They also sell on eBay as do other chemical suppliers. Seek and ye shall find though it’s harder in some countries than others.

If you choose to buy some isopropyl alcohol you should now realise that you can, if you wish, do things lilke dilute it with water and perhaps add some white vinegar to make your own version of the Spartan glass cleaner type of product. But I find it is best when the isopropyl alcohol is used at full strength and pure because it evaporates quickly and cleanly.

You may also choose to buy some acetone. I find it will deal with contaminants that isopropyl alcohol struggles with (and vice versa). I always use it neat as it evaporates very quickly and cleanly.

Don’t waste your money on branded products when you know about cheaper and better alternatives!

A Curious Detour

Although a detour, it is interesting to look here because it says

“I’ve been told that [Fusemaster] Superspray has a shelf life of about 1 1/2 years. If that is true, and yours is fairly old, that might be the cause [of devitrification]”.

Well, a search for the MSDS for this devitrification spray tells me it’s pretty-much powder frit added to ethyl alcohol with a tiny amount of isopropyl alcohol with some methyl isobutyl ketone as a surfactant. What struck me as interesting is that the three chemicals used to “carry” the glass powder seem to be remarkably similar to what we’d expect for a glass cleaning product. I can see the logic for using the two alcohols but I’m baffled why the surfactant is used, other then perhaps they are simply mixing a bought-in glass cleaning product and mixing it with clear glass powder frit.

But back to the context of the original forum posting… Call me stupid if you like but I don’t think powdered frit has a shelf life. And I don’t ever recall seeing a “Best before” date on any window cleaning product I’ve ever seen in the past. In other words the devit spray can’t be the cause of the devitrification.

Another example of well-meant poor advice I think!

And Finally

That’s all my chatter for today so all that remains is to remind all you “do it yourself” fans that I’ve already done postings that tell you how to make your own copper patina solution, safety flux and glass polishing compound.

Best wishes and a happy new year to you all.

Posted in Glass Cleaning, Money-saving ideas | Tagged , , | Leave a comment

Undercut Your Dichro

Today’s blog is mercifully short. There’s no maths or science and it isn’t even a fantastic new discovery that will change the world. It’s more of a helpful tip to those who’ve maybe not realised there’s an answer to the following problem:

When firing a piece of  clear-backed dichroic glass metal side down over a base of some other kind of glass we can produce a three-dimensional “well” effect. The problem is that it results in a messy-looking metal edge when we take it out of the kiln.

On the right is a picture of what I mean.

The left side illustrates what you can expect to happen without today’s tip. The right side shows that the problem can be managed, albeit not perfectly in this particular example.

Although I earn no gold star for excellence with this particular experiment you can at least see there’s a distinct improvement. The questions to be answered are how the problem arises and how the problem can be eliminated or at least mitigated.

The problem arises because the clear-backed dichroic glass sinks into the glass base during the fusing process and leaves behind some of the metal layer at the edges.

The answer to this problem is simple. Just grind away the dichroic metal layer from the edges of the piece of dichroic glass. This can be done very quickly with diamond pads for untextured dichroic glass but will be more fiddly with textured surfaces.

To illustrate what you are aiming for, look at the diagram below. The lower area represents the base glass, the upper area represents the clear dichroic glass and the thick line represents the metal layer of the dichroic glass.

Notice the angled undercutting at the lower edges of the dichroic glass and how some of the metal layer gets removed as a consequence. From this you will realise it’s not the angle of the undercutting that is important but the amount of metal layer that gets removed. Having said that, you’ll get better control over how much metal you remove with a reasonable angle that you’ll achieve with a really shallow angle.

Exactly how much undercutting is needed to eliminate the problem primarily depends on the thickness of the dichroic glass layer. I also expect (but have not checked) that the amount of undercut will also depend on whether you are using a microwave kiln or a “proper” kiln. Start with a couple of millimetres of undercutting for your first experiment. Let practise and experience become your teacher.

That’s all for now. Happy fusing.


Posted in Dichroic Glass, Microwave kiln | Tagged , , | Leave a comment

The Glass Bookshelf

For your enjoyment I have gathered together details of well over a hundred old books that relate to glass in some form or another, all of which are easily accessible over the Internet.

Whether it’s the glass sands of Kentucky, glass manufacture, glass painting, old trade catalogues, collecting glassware, making laboratory glassware, old Church windows or one of the many other strange topics relating to glass, there’s surely something for you somewhere in the list. I hope you find something that tickles your fancy.

Downloadable Book Lists

Although you’ll find the book list below within this blog I’m sure that some of you will want to “do your own thing”. So, I’ve created three alternative files that you can download and fiddle with. You could then sort your copy of the book list by title, date or author, improve the topic lists, add more books, or whatever else you might fancy doing. Make the downloaded files your own personalised bookshelf!

Beware: Although the file names below have familiar file types like “.doc” and “.pdf”, they aren’t what they seem to be. I’ve had to do some simple “trickery” to enable you to download file types that WordPress, in its infinite wisdom, has chosen not to allow. So, be sure to read the text that follows the filenames before downloading them!

  • Bookshelf-rtf.doc   Actually this is not a “.doc” file, it’s a “.rtf” file. I had to rename it from “Bookshelf.rtf” to “Bookshelf-rtf.doc” before WordPress would to allow me to share it with you. So, please rename it back to “Bookshelf.rtf” once you’ve downloaded it. Let me explain… Unlike “.doc” files, “.rtf” rich text files are Microsoft’s only official “portable” file format for word processing documents. This means it can be loaded into many kinds of word processor applications and not just Microsoft Word. Use this file if you want to maintain and use the book list within your word processor. If this doesn’t work for you then try the Bookshelf.xls file format in your spreadsheet application and copy the table out of there into your word processor application.
  • Bookshelf.xls   This spreadsheet file really is an “.xls” file and it is saved in an old version of Microsoft Excel format so you don’t need Microsoft’s latest and greatest bloatware to use this file. It should work with some other spreadsheet applications too.  Use this file if you want to maintain and use the book list as a spreadsheet. If this doesn’t work for you then try the Bookshelf.tsv file instead (see below).
  • Bookshelf-tsv.pdf   Actually this is not a “.pdf” file, it’s a “.tsv” file. I had to rename it from “Bookshelf.tsv” to “Bookshelf-tsv.pdf” before WordPress would to allow me to share it with you. So, please rename it back to “Bookshelf.tsv” once you’ve downloaded it. This is a “tab separated variable” file that can be loaded into most kinds of spreadsheet application, word processors and even some database applications. Treat this as your “last chance” file format because you’ll probably need to do some messing about to get what’s loaded into a nice useful state. Despite this it’ll be much quicker than trying to type everything manually.

If you struggle and fail with all three file formats, or have a particular need for some other file format for use on something other than a Microslop Windoze machine then do let me know and I’ll try to help.

Some Notes

The Title, Author and Date columns should uniquely and correctly identify each book but in some cases notes are added in square braces within the Title column to indicate something noteworthy, such as telling you that a different edition elsewhere in the table. Where a the title of a book title contains an ellipsis it is an indication that the full title was so long and verbose that it has been truncated. There were occasions when I reckoned the book details didn’t seem to be correct (for whatever reason) so occasionally you’ll find that information about titles, authors or dates in my table are not quite what you’ll find at

The Topics column gives an indication of what kind of information is found in the books and can be rather vague. Sometimes I’ve given you what the archivist recorded as the topics, if anything. Sometimes I’ve added to their topic lists and sometimes I had to create the topic list myself. A consequence is that the list of topics can be rather erratic but better than a poke in the eye with a blunt stick.

The Location column contains one or more URL links that take you to a web page where you can download the book. It’s perhaps sad to note that many of the old books have been digitised multiple times whereas many other old books remain only as “hard copy”. After awhile I got bored with finding alternative sources for the books so stopped bothering.

In all cases, visiting the URL will reveal a download available in PDF format. Often there are other file formats available as well. Alternative formats might be more suitable for use on a Kindle or mobile phone, for example. If you intend to download a copy of all the books in PDF format then you will need about 4GB of free disk space.

Bear in mind that copyright laws in different countries are not the same. Distributing this list of books and their locations will not breach any copyright but distributing the scanned book images and expecting payment might.

Here are the books I’ve found so far. There are even more out there!

Oh, and sorry about the bad layout of the table. Despite messing around with the undelying HTML I can’t force WordPress to present the information tidily.

Title Author Date Topics Location
The Glass Worker, vol 4 no 46 (Jun 1907) and vol 4 no 48 (Aug 1907) Amalgamated Glass Workers’ International Association of America 1907 Glass Industry, Industrial
A Notable Collection of Ancient Egyptian, Greek and Roman Glass, Persian Potteries, Greek Painted Vases … Anderson Galleries Inc. 1924 Mr. Azeez Khayat, Catalogue
Stained glass of the middle ages in England & France Arnold, H. 1913 Glass painting and staining, Art, Mediaeval, England, France. and similar at
Arts and crafts essays

[in which many subjects are covered, including Stained Glass by Somers Clarke, pp96-105)

Arts and Crafts Exhibition Society 1893 Arts and crafts movement, Decorative arts
History of the Worshipful Company of Glaziers of the City of London, otherwise the Company of Glaziers and Painters of Glass Ashdown, C. H. 1919 Company of Glaziers, London, Guilds.
Twelfth Census of the United States: Census Bulletin no 228: Manufactures: Glass Manufacture Austin, S. P. 1902 Glass industry, Census
The painter, gilder, and varnisher’s companion containing rules and regulations in everything relating to the arts of painting, gilding, varnishing, and glass staining … [See also 1867 edn] Baird, H. C. (Pub.) 1850 Painting, Industrial, Gilding, Varnish and varnishing, Receipts.
The painter, gilder, and varnisher’s companion containing rules and regulations in everything relating to the arts of painting, gilding, varnishing, and glass staining …, 10th Edn.

[See also 1850 edn]

Baird, H. C. (Pub.) 1867 Painting, Industrial, Gilding, Varnish and varnishing, Receipts.
Schwäbische Glasmalerei Balet, L. 1912 Glass painting and staining
A Treatise on Painted Glass, Shewing its Applicablity to Every Style of Architecture Ballantine, J. 1845 Glass painting and staining
American glassware, old and new: a sketch of the glass industry in the U.S. and manual for collectors of historical bottles Barber, E. A. 1900 Glass manufacture, Glassware
Spanish Glass in the Collection of the Hispanic Society of America Barber, E. A. 1917 Glassware, Spain
English table glass

[See also later edition]

Bate, P. H. 1905 Glassware, Tableware, England
English table glass

[See also earlier edition]

Bate, P. H. 1913 Glassware, Tableware, England
President’s Address on “Stained Glass and Painted Glass” , in Transactions of the Bristol and Gloucestershire Archaeological Society, Vol 22. Editor: Rev. C. S. Taylor, Bazley, G. S. 1899 Periodical. Antiquities, Bristol and Gloucestershire, Glass painting and staining.
Catalogue Belcher Mosaic Glass Co. 1886 Mosaics, Glass painting and staining, Glass, Coloured–Catalogues
A lecture on stained glass Bell, R. 1922 Glass painting and staining
Sir Henry Bessemer, F. R. S. An autobiography

[Chapter VIII relates to glass processing]

Bessemer, H., Sir. 1905 Glass manufacture, Industrial processes, Autobiography
Elements of Glass and Glass Making Biser, B. F. 1899 Glass manufacture
The Art of Glass: shewing how to make all sorts of glass, crystal and enamel, likewise the making of pearls, precious stones, china and looking-glasses … [Translation of: De l’art de la verrerie] Blancourt, H. 1699 Glass manufacture, Enamels & enamelling, precious stones, minerals, optical glass, glass eyes
A handbook of laboratory glass‐blowing Bolas, B. D. 1921 Glass blowing and working, Glass manufacture, Technique
A memoir on British resources of sands suitable for glass‐making Boswell, P. G. H. 1916 Glass manufacture
Japanese Enamels: With Illustrations from the Examples in the Bowes Collection Bowes, J. L. 1886 Enamels and enamelling, Cloissonné, Shippo, Japan
Notes on Shippo: A Sequel to Japanese Enamels Bowes, J. L. 1895 Enamels and enamelling, Glass manufacture, Cloissonné, Shippo, Japan
Glass cup plates: A Guide to Collectors Burns, C. 1921 Glassware
Storied windows: A traveller’s introduction to the study of old church glass, from the twelfth century to the Renaissance, especially in France Bushnell, A. J. 1914 Glass painting and staining, Cathedrals, Renaissance, Mediaeval, France
Catalogue of the collection of stained and painted glass in the Pennsylvania museum Bye, A.E. 1925 Glass painting and staining, Philadelphia Museum of Art
General Electric Lighting Canadian General Electric Company 1949 Lighting, Glassware, Commercial & industrial equipment.
Stories of Industry, 1891, Vol 1

[Vol 2 relates to clothing and foodstuffs]

Chase, A. & Clow, E. 1891 Industrial Arts, Minerals, Industrial Processes, Machinery & Equipment, Glass Manufacture, Pottery manufacture
Art glass metals Chicago Metallic Sash Company 1925 Art glass, Came, Stained Glass, Glazing accessories, Trade, Catalogues
Five Black Arts: a popular account of the history, processes of manufacture, and uses of printing, pottery, glass, … Coggeshall, W. T. 1861 Printing History, Porcelain History, Glass Manufacture History, Iron Industry and Trade History, Gas Manufacture and Works History
The Crown Glass Cutter and Glazier’s Manual: Glass cutter, glazier & stained glass maker in ordinary to the king for Scotland Cooper, W. 1835 Glass manufacture
Windows: A Book about Stained & Painted Glass

[See also later edition]

Day, L. F. 1897 Glass painting and staining and also
Windows: A Book about Stained & Painted Glass

[See also older edition]

Day, L. F. 1909 Glass painting and staining
Catalogue of an Exhibition of Stained Glass from the XIth to the XVIIIth cent Demotte Inc. (Pub.) 1920 Glass painting and staining
Glass Dillon, E. 1907 Glass, Glassware
A history of English glass painting, with some remarks upon the Swiss glass miniatures of the sixteenth and seventeenth centuries Drake, M. 1912 Glass painting and staining
Valuable secrets in arts, trades, &c.: selected from the best authors and adapted to the situation of the United States [See also other editions] Duyckinck, E. (Pub.) 1802 Receipts, Workshop recipes, Industrial art, Art technique
Valuable secrets in arts, trades, &c.: selected from the best authors and adapted to the situation of the United States. [See also other editions] Duyckinck, E. (Pub.) 1809 Receipts, Workshop recipes, Industrial art, Art technique
Valuable secrets in arts, trades, &c.: selected from the best authors and adapted to the situation of the United States [See also other editions] Duyckinck, E. (Pub.) 1816 Receipts, Workshop recipes, Industrial art, Art technique
Ancient stained and painted glass Eden, F. S. 1913 Glass painting and staining, History
The collection of heraldic stained glass at Ronaele Manor, Elkins Park, Pennsylvania, the residence of Mr. & Mrs. Fitz Eugene Dixon Eden, F. S. 1927 Dixon, Fitz Eugene, Glass painting and staining, Heraldry, Devices
Graeco‐Egyptian Glass Edgar, C. C. 1905 Ancient Glassware, Greco-Egyptian Glassware
The Origin of Glass Blowing in American Journal of Archaeology, Vol XX, pp 134-143 Eisen, G. 1916 Glass blowing
Antique Glass, in The Art Bulletin, Vol2: pp 87-119. Eisen, G. A. 1919 Glass painting and staining
Stained glass windows: An essay with a report to the vestry on stained glass windows for Grace Church, Lockport, New York Faber, W. F. 1900 Grace Episcopal Church (Lockport, N.Y.), Church records and registers, Glass painting and staining, Genealogy
Notes on the Painted Glass of Canterbury Cathedral Farrar, F. W. 1897 Canterbury Cathedral, Glass painting and staining
Glass Manufacture and the Glass Sand Industry of Pennsylvania Fettke, C. R. 1919 Glass, Glass manufacture, Glass Sands, Pennsylvania and at
The drama of glass [Publication date uncertain but there are references to 1893 within text] Field, K. 189‐ Glass manufacture
Hiersemanns Handbücher, Vol VIII: Handbuch der glasmalerei für forscher, sammler und kunstfreunde, wie für künstler, architekten und glasmaler Fischer, J. L. 1914 Glass painting and staining.
Laboratory manual of glass‐blowing Frary, F. C. 1914 Glass Manufacture, Glass-Blowing, Scientific Glassware, Laboratory, Technique
An Essay on the Art of Painting on Glass from the German of Emanuel Otto Fromberg Fromberg, E. O. 1851 Glass painting and staining
Rudimentary Essay on the Art of Painting on Glass from the German of Emanuel Otto Fromberg Fromberg, E. O. 1857 Enamel and enamelling, Glass painting and staining, Glass manufacture chemistry
Histoire de la Verrerie et de l’Émaillerie Garnier, E. 1886 Glass painting and staining, Enamel and enamelling
Street Lighting Glassware General Electric Company 1925 Street lighting, Glassware
Metal Casements and Frames, Wrought Iron George Wragge Ltd. 1948 Steel windows, casement windows, Trade catalogue
Rudimentary treatise on the art of painting on glass or glass-staining: comprising directions for preparing the pigments and fluxes … Gessert, M. 1851 Enamel and enamelling, Glass painting and staining and similar at
A booke of sundry draughtes, principaly serving for glasiers … Gidde, W. 1615 Decoration and ornament, Glass painting and staining, Enamel and enamelling
Stained Glass and Metal Work of Every Description for Churches, Chapels, etc.: Catalogues, Photographs and Special Designs with… Gorham Manufacturing Co. 1895 Trade catalogue, Stained Glass, Art Glass, Ecclesiastical, Windows, Memorials,
Le Vetrate di S. Francesco in Assisi – Studio Storico Iconografico Guisto, E. M. 1911 San Francesco Church (Assisi, Italy), Glass painting and staining
Old English glasses. … glass drinking vessels in England, from early times to the end of the eighteenth century Hartshorne, A. 1897 Glassware, Great Britain, Old English Glass, Jacobite Glass, Irish Glass, Wine in England
An history of the origin and establishment of Gothic architecture : comprehending also … Hawkins, J. S. 1813 Cesare Cesariano, Glass painting and staining in Middle Ages, Gothic Architecture
Rich cut glass and fine china Higgins & Seiter 1903? Trade Catalogue, Porcelain, Glass, Cut Glass
General catalogue of the manufactures of Adam Hilger, Ltd Hilger, A. 1913 Wavelength Spectrometers, Optical instruments, Scientific instruments
Stained glass as an art Holiday, H. 1896 Glass painting and staining
A practical manual of the collodion process : giving in detail a method for producing positive and negative pictures on glass and paper, ambrotypes, printing process, also patents… Humphrey, S. D. 1857 Collodion process, Collodion process, Photography, Photographic chemistry
Invisible Glass Windows: A Dramatic New Merchandising Force

[An example of this can be seen in Byram Street, Huddersfield, West Yorkshire]

Invisible Glass Company of America 1937 Trade catalogue, Store front, Display window.
Encyclopaedia of chemistry, theoretical, practical, and analytical, as applied to the arts and manufacturers J. B. Lippincott & Co. 1877 Chemistry, Technical, Art, Manufacturing
Glass: Interesting Facts connected with its Discovery and Manufacture J. E. Caldwell & Co. 18?? Glassware, Trade Catalogues, Glass History, Cut Glass
Priced and Illustrated Catalogue of Optical Instruments, Made, Imported and Sold, Wholesale and Retail James W. Queen & Co. 1870 Trade Catalogue, Optical Instruments, Lenses, Spectacles, Eye-Glasses, Telescopes, Camera Obscura, Microscopes, Dissection Tools, Biological Specimens, Geological Specimens
Reminiscences of glass‐making, 2nd Edn. Jarves, D. 1865 Glass Manufacture, Glass History, Chemistry, Workshop, Recipes
L’art de la Peinture sur Verre et de la Vitrerie Le Vieil, P. 1774 Glass painting and staining
Valuable secrets concerning arts and trades

[Note: T. Hubbard is the publisher, not the author]

Leather, V. 1795 Decorative Arts and similar at
Department Store Mechandise Manuals: The Glassware Department Lehmann, M. A. 1918 Glassware, Glassware manufacture
Old glass and how to collect it

[See also later editions]

Lewis, J. S. 1900 Glass collecting, Glassware
Old glass and how to collect it

[See also earlier edition]

Lewis, J. S. 1916 Glass collecting, Glassware
Old glass and how to collect it

[See also earlier editions]

Lewis, J. S. 1950 Glass collecting, Glassware
Flat Glass Libbey‐Owens‐Ford Glass Company 1924 Glass, Glazing, Trade Catalogue, Glass manufacture
Experimental Glass Blowing for Boys Lynde, C. J. 1920 Glass blowing and working, Laboratory
Fifty years of glass making, 1869‐1919 Macbeth‐Evans Glass Company 1920 Glass Manufacture
Glass and glass manufacture Marson, P. 1919 Glass, Glass manufacture
Optical measuring instruments, their construction, theory, and use Martin, L. C. 1924 Optical Instruments, Optical devices, Optics, Engineering
American glass McClinton, K. 1950 Glassware
Les Vitraux Merson, O. 1895 Glass painting and staining and also at
Fifteenth-Century Glass in The Chancel Window of St. Peter Mancroft, Norwich Meyrick, F. 1911 St. Peter Mancroft Church (Norwich, England), Glass painting and staining
Stained glass Miller, E. 1900 Glass painting and staining
Window Glass in the Making: An Art, A Craft, A Business Monroe, W. L. 1926 Glass, Glazing, Industrial Arts
The secret of pictorial art, or Self instructor in painting on glass, china, satin, and paper … Morse, D. D. 1879 Decorative arts, Decoration and ornament, Painting, Drawing
International Art Glass Catalogue: Art and bevelled glass in all its branches: church, memorial, society and domestic windows, Art Nouveau, prism, mitre beveled plate, leaded bevel, etc. [See also 1924 edition] Nat. Ornamental Glass Mfrs Assn of the US and Canada. 1914 Glass painting and staining, Catalogues, Trade catalogue, Art glass
Revised International Art Glass Catalogue: Art and bevelled glass in all its branches: church, memorial, society and domestic windows, Art Nouveau, prism, mitre beveled plate, leaded bevel, etc. [See also 1914 edition] Nat. Ornamental Glass Mfrs Assn of the US and Canada. 1924 Glass painting and staining, Catalogues, Trade catalogue, Art glass
Ancient painted glass in England 1170-1500 Nelson, P. 1913 Glass painting and staining, England, Mediaeval.
A descriptive catalogue of the glass vessels in the South Kensington museum Nesbitt, A. 1878 Glassware
Glass Nesbitt, A. 1878 Glass, Glassware, History, Glass Composition
Geschichte der Schweizer Glasmalerei Oidtmann, H., Dr. 1905 Glass painting and staining
Die Rheinischen Glasmalereien vom 12. bis zum 16. Jahrhundert, Erster Band Oidtmann, H., Dr. 1912 Glass painting and staining
Modern optical instruments and their construction Orford, H. 1896 Optics, Optical Instruments, Optical devices.
Le Vitrail; Son Histoire, Ses Manifestations à Travers les âges et les Peuples Ottin, L. 1896 Glass painting and staining
The Arcana of Arts and Sciences: or Farmers’ & Mechanics’ Manual: containing a great variety of valuable receipts and useful discoveries… Parker, M., Dr. 1824 Formulae, Recipes, Receipts, Agriculture, Industrial Arts, Pigments, Dyes, Dyeing, Woods, Metallurgy, Stains, Varnish, Glass manufacture, Cements, Enamelling
Curiosities of glass making: With details of the processes and productions of ancient and modern ornamental glass manufacture Pellatt, A. 1849 Glass manufacture, Anceint glassware, Technique
The glass collector; A Guide to Old English Glass Percival, M. 1919 Glassware
The amateur’s handbook of practical information for the workshop and the laboratory, 2nd Edn. Phin, J. 1879 Workshop, Laboratory, Recipes. and at
Glass, paints, oils and painters’ sundries Pittsburgh Plate Glass Company 1901 Trade Catalogue, Art materials, Glass, Ornamental
Glass, Paints, Varnishes and Brushes: their history, manufacture, and use Pittsburgh Plate Glass Company 1923 Glass, Glazing, Mirrors, Plate glass, Leaded glass, Store front, Commercial furniture, Pittsburgh Plate Glass Company
Old Beauty in New Glass Pittsburgh Plate Glass Company 1930 Trade catalogue, Glass, Ornamental glass, Windows, Art glass, Stained Glass
A treatise on the origin, progressive improvement, and present state of the manufacture of porcelain and glass Porter, G. R. 1832 Porcelain, Glass manufacture and similar at
The Rudiments of Mineralogy, 3rd Edn. Ramsay, A. 1885 Mineralogy, Rocks & Minerals
The Glass Sands of Kentucky: A Detailed Report Covering the Examination, Analysis and Industrial Evaluation of the Principal Glass Sand Deposits of the State Richardson, C. H. 1920 Rocks & Minerals, Sand, Glass manufacture
Glorious Glass at St. John’s Church, Gouda Rijksen, A. A. J. 1900 Sint Janskerk (Gouda, Netherlands), Glass painting and staining
Glass Manufacture Rosenhain, W. 1919 Glass manufacture
Vasily Kandinsky painting on glass (hinterglasmalerei) Anniversary Exhibition Rothel, H. K. 1966 Wassily Kandinsky, Glass painting and staining, Stadtische Galerie in Munich
Structure and Kinetics of Glass Corrosion [D.Phil Dissertation] Sanders, D. M. 1973 Glass, Glass corrosion
La Verrerie depuis les Temps les Plus Reculés Jusqu’à nos Jours

[See also 1869 edn]

Sauzay, A. 1868 Glass, Glassware, Glass manufacture, Glass craft, Decoration and ornament, Glass painting and staining, Mirrors, Optical glass, Optical instruments, Eyes, Artificial, Glass beads
La Verrerie depuis les Temps les Plus Reculés Jusqu’à nos Jours, 2nd Edn.

[See also 1868 edn]

Sauzay, A. 1869 Glass, Glassware, Glass manufacture, Glass craft, Decoration and ornament, Glass painting and staining, Mirrors, Optical glass, Optical instruments, Glass eyes, Glass beads, Pigments, Water colours, Cosmetics, Fabrics and dying,
Wonders of Glass‐Making in All Ages Sauzay, A. 1870 Glass manufacture, Glassware
Marvels of Glass‐Making in All Ages Sauzay, A. 1870 Glass, Glass manufacture
Handbook of the Glass Industry Scholes, S. R. 1941 Glass manufacture, Chemistry, Physics, Orton Cones, Recipes, Conversion tables, Commercial advertising
Recipes for Flint Glass Making: being leaves from the mixing book of several experts in the flint glass trade…, 2nd Edn. Scott, Greenwood & Son (Pub.) 1907 Glass, Workshop recipes
General Catalog 1911-1912

[Mostly wood-related]

Segelke & Kohlhaus Mfg. Co. 1912 Trade Catalogue, Wooden fittings, Wood windows, Commercial fixtures, Art glass, Stained Glass
The chemistry of the several natural and artificial heterogeneous compounds used in manufacturing porcelain, glass, and pottery

[Originally published 1837]

Shaw, S. 1900 Pottery, Chemistry, Technical
The Methods of Glass Blowing ‐ For the use of physical and chemical students Shenstone, W. A. 1897 Glass blowing and working
The Methods of Glass Blowing, and of Working Silica in the Oxy‐Gas Flame: For the use of chemical and physical students [see also 1916 edn’ Shenstone, W. A. 1902 Glass blowing and working
The Methods of Glass Blowing, and of Working Silica in the Oxy‐Gas Flame: For the use of chemical and physical students [see also 1902 edn’ Shenstone, W. A. 1916 Glass blowing and working
Stained glass tours in France Sherrill, C. H. 1908 Glass painting and staining, Church buildings, Cathedrals, France, Travel
Stained glass tours in England Sherrill, C. H. 1909 Glass painting and staining, Church buildings,Cathedrals, England, Travel
A stained glass tour in Italy Sherrill, C. H. 1913 Glass painting and staining
Photography in a nut shell; or, The experience of an artist in photography, on paper, glass and silver, with illustrations. Simons, M. P. 1858 Photography, Photographic chemistry, Daguerreotype, Ambrotype
The Laboratory, or, School of Arts: Containing a large collection of valuable of secrets, experiments, and manual operations in arts and manufactures… Vol II, 6th Edn.

[See also Vol I]

Smith, G. 1799 Industrial Arts, Technology, Receipts, Recipes, Coins, Medals, Drawing, Painting, Gnomonics, Optics, Etching, Engraving, Paint pigments, Varnish
The Laboratory, or, School of Arts: Containing a large collection of valuable of secrets, experiments, and manual operations in arts and manufactures… Vol I, 6th Edn.

[See also Vol II]

Smith, G. 1799 Industrial Arts, Technology, Receipts, Recipes, Fireworks, Metallurgy, Glass making, Glass staining and painting, Metal casting,
Practical instructions in enamel painting on glass, china, tiles, etc … Snell, H. J. 1874 Glass painting and staining, China painting, Enamel and enamelling, Artists’ materials
The golden cabinet : being the laboratory, or handmaid to the arts : containing such branches of useful knowledge, as nearly concerns all kinds of people, from the squire to the peasant, and will afford both profit and delight Spotswood, W. 1793 Chemistry, Technical, Industrial arts, Technical manuals, Formulas, Recipes, Gilding, Glass, Drawing, Dyes and dyeing, Japanning and similar at
Decoration of Metal, Wood, Glass, etc.: A book for manufacturers, mechanics, painters, decorators,… Standage, H. C. 1908 Workshop recipes, receipts, Metal, Glass
Old Irish glass Stannus, G. 1921 Glassware, Irish
Procedures In Experimental Physics Strong, J. 1938 Experimental Physics, Laboratory, Glass blowing, Optics, Heat, Radiation, Vacuum, Moulding and casting
A Treatise on the Art of Glass Painting Suffling, E. R. 1902 Glass painting and staining
Memorial windows Tiffany Glass & Decorating Co. 1896 Glass painting and staining, Favrile glass, Catalogues, Trade catalogues
Tiffany Favrile Glass, Tiffany Windows, Tiffany Mosaics, Tiffany Monuments, Tiffany Granite [see also later edition] Tiffany Studios 1913 Catalogues, Mosaics, Glass painting and staining, Memorials, Sepulchral monuments.
Tributes to honor, suggested types of memorials by the ecclesiastical department of the Tiffany Studios. Tiffany Studios 1918 Catalogues, Glass paining and staining, Sepulchral monuments.
Tiffany Favrile Glass, Tiffany Windows, Tiffany Mosaics, Tiffany Monuments, Tiffany Granite [see also earlier edition] Tiffany Studios 1922 Catalogues, Mosaics, Glass painting and staining, Memorials, Sepulchral monuments.
Art in Glass: A guide to the glass collections Toledo Museum of Art 1969 Glass art
Philological Studies in Ancient Glass

[1922 PhD Thesis]

Trowbridge, M. L. 1930 Greek language, Latin language, Classical literature, Glass Manufacture, Glass uses, Glass
On some Optical Peculiarities of Ancient Painted Glass, in Proceedings of the Clifton Antiquarian Club for 1884/88-1909/12, Vol 1, pp 207-216.

[Appears to be the same as the book of the same name]

Tuckett, F. F. 1888 Trademarks, Merchants
On some Optical Peculiarities of Ancient Painted Glass. Offprint from VClifton Antiquarian Club. Tuckett, F. F. 1888 Glass painting and staining, Medieval
Journal of the Society of Glass Technology, Vol IV Turner, W. E. S. (Ed) 1920 Journal, Technical, Glass Technology
Journal of the Society of Glass Technology, Vol V Turner, W. E. S. (Ed) 1921 Journal, Technical, Glass Technology
Journal of the Society of Glass Technology, Vol VI Turner, W. E. S. (Ed) 1922 Journal, Technical, Glass Technology
Journal of the Society of Glass Technology, Vol VII Turner, W. E. S. (Ed) 1923 Journal, Technical, Glass Technology
Chemical analysis for glassmakers: Containing methods of analysis for clays and other silicates which will be found useful for the pottery industry Uhlig, E. C. 1903 Glass manufacture, Chemical analysis,
The glass industry. Report on the cost of production of glass in the United States United States Bureau of Foreign and Domestic Commerce 1917 Glass manufacture, Industry, Glass industry
Information Concerning Optical Glass and Chemical Glassware United States Tariff Commission 1919 United States, Glassware, Glass manufacture, Optical glass, Trade Tariffs
Notice historique sur les Peintres-Verriers d’Anvers du XVe au XVIIIe Siècle van Cauwenberghs, C. 1891 Glass painting and staining
University of Illinois Engineering Experiment Station Bulletin No. 118, December 1920, Dissolved Gases in Glass Washburn, E. W., Footitt, F. F. and Bunting, E. N. 1920 Glass manufacture, Glass chemistry
Report on the Manufacture of Glass Weeks, J. D. 1883 Glass Manufacture, Glass-working, Glass composition, Report, Statistics, 1880 Census, United States,
Stained glass; a handbook on the art of stained and painted glass, its origin and development from the time of Charlemagne to its decadence (850-1650 A. D.) Werck, A. 1922 Glass painting and staining, Mediaeval, Art
Irish Glass: An account of glass‐making in Ireland from the XVIth century to the present day Westropp, M. S. D. 1920 Glass, Glass manufacture, Ireland
Stained glass work: a text-book for students and workers in glass.

[part of The Artistic Crafts Series of Technical Handbooks, ed. W. R. Lethaby]

[See also 1905 edition’

Whall, C. W. 1920 Glass painting and staining, Glass manufacture, Technique and similar at and at
Stained glass work: a text-book for students and workers in glass

[part of The Artistic Crafts Series of Technical Handbooks, ed. W. R. Lethaby]

[See also 1920 edition]

Whall, C.W. 1905 Glass painting and staining, Glass manufacture, Technique
A concise account of the principal works in stained glass that have been executed Willement, T. 1840 Glass painting and staining — Great Britain
William Morris & Compy (Ruskin House) Ltd William Morris & Co. 1910 Windows, Glazing, Glass, Stained Glass, Casement windows, ornamental metals, Trade Catalogue
Notes on the development of the ruby color in glass in University of Illinois Bulletin Vol XI No. 23, 30 July 1914 Williams, A. E. 1913 Glass, Glass chemistry, Ruby
An inquiry into the difference of style observable in ancient glass paintings: especially in England: With Hints on Glass Painting, Vol. 1

[See also Vol 2]

Winston, C. 1847 Glass painting and staining and similar at and at
An inquiry into the difference of style observable in ancient glass paintings, especially in England with hints on glass painting, Vol. 2

[See also Vol 1]

Winston, C. 1847 Glass painting and staining and similar at
Memoirs illustrative of the art of glass painting Winston, C. 1865 Glass painting and staining and similar at
One Thousand Valuable Secrets in the Elegant and Useful Arts, Collected from the Practice of the Best Artists, and … Woodward, W. W. 1795 Receipts, Recipies, Art materials, Cooking, Industrial Arts, Formulae, Engraving, Metallurgy, Varnish, Glass Manufacture, Glass painting,
The Manufacture of Optical Glass and of Optical Systems: A war-time problem Wright, F. E. 1921 Optical instruments, Optical glass, Glass manufacture
Manual of Laboratory Glass Blowing Wright, R. H. 1943 Glass Blowing, Technique
Collecting old glass: English and Irish Yoxall, J. H. 1916 Glass collecting, Glassware

Well that’s all folks. Happy reading!

Posted in Books | Tagged | Leave a comment

Thickening Glastac

Today I want to have a short chat about my experiences with Bullseye’s Glastac and some experiments with using CMC to thicken it. There’s no rocket science. I simply though you might enjoy another way to make use of your CMC.


If you’re a glass fuser you’ve probably used Glastac. If you haven’t I recommend you try it.

Glastac is a deliberately weak glue and in my experience it cleanly burns away in a kiln. It is useful because you can glue together the component parts of your glass masterpiece with the certain knowledge that you can re-place the parts for quite a long time. Better still, it helps to ensure your masterpiece will not fall apart when you are moving it to your kiln.

As an aside, I caution against using white PVA glues, such as the oft-recommended Elmer’s Glue. Although I do use PVA glues occasionally, I have noticed that it does not always cleanly burn away and that it can cause damage to a glass surface. I particularly notice this when an excess of PVA is used. But I digress.

The only problem I have found with Glastac, particularly when used in excess, is that surface tension sometimes drags small pieces of glass away from where I put them. Using less Glastac helps avoid this problem but the converse situation is that sparing use of Glastac means that the small pieces of glass are not sufficiently glued to stay put.

And then I noticed that Bullseye had introduced Glastac in a gel form. Hmm. Thinks. Can I find the Manufacturer’s Safety Data Sheet (MSDS) to find out how it differs from the “old fashioned” Glastac? No, so it’s time to just experiment.

Avid readers amongst you will remember that I’ve chattered about carboxymethylcellulose (CMC) on a number of occasions. Most of my chatterings were in Squirt Your Frits but I’ve also mentioned it in passing in other places such as converting ordinary safety flux into a gel form over at Make Your Own Safety Flux.

This made me wonder if a little CMC gloop would thicken “old fashioned” Glastac and make it even better.

Thickening Your Glastac

dscf3558-glastacInstructions on where to find CMC, what it is, how it works and how to make your own CMC gloop is covered in plenty of detail over in my Squirt Your Frits blog. I will not repeat all this information so read that blog and come back again if you need to. I will however show you pictures of a bottle of Glastac and (lower down) a little 100 gram pot of CMC sold under the “Tylo” brand name typically bought by sugar crafters.

Making your own substitute for Bullseye’s Glastac Gel is a simple matter of thickening up some “old fashioned” Glastac with CMC. However the devil is, as they say, in the detail.

I found it most convenient to start by making up some “sloppy” sol-phase CMC gel. The exact consistency does not matter. All you are aiming for is a CMC gel that is thick but flows reasonably slowly when you tip the container.

dscf3555-cmc-potNext, you need to find another little container and add some Glastac to some CMC gel and give it a thorough mixing. If the outcome is too thick, either add some more Glastac or add some water. If the outcome is too runny add some more CMC gel.

As to the exact proportions of Glastac and CMC gel I can only report that making numerous little batches with differing proportions didn’t make seem to make any noticeable difference. As long as there’s a reasonable amount of Glastac in the mixture it’s going to be a glue. As long as there’s some CMC gel in the mixture it’s going to be thicker.

What could be simpler than that?

Speedy Gel?

In an attempt to make the homemade substitute dry quicker I tried using propanol in place of some of the water.

There’s nothing special about propanol (also known as isopropyl alcohol). It’s just an industrial alcohol  that is widely used as a solvent and as such it’s also useful for cleaning glass. Having said that, I mostly use acetone for cleaning glass.

However, unlike the ethanol (also known as ethyl alcohol) in your booze, it’s not safe to drink. Here in the UK I buy it from APC Pure rather than from glass suppliers simply because it’s much cheaper and they’re relatively local. I’m not connected with APC Pure other than being a customer. And once again, I digress…

I didn’t notice any adverse effects of using this modified mixture other than the smell of evaporating propanol. I can’t really say that I noticed the glue drying noticeable quicker but to be fair I wasn’t conducting a proper controlled experiment against a stopwatch.

So, I leave you with the thought that using an alcohol, such as propanol, should quicken the rate at which the glue dries but no convincing practical evidence. This is a prompt for you to continue the experiment and tell me!

Homemade Glastac Gel In Use

Although I have not compared this homemade Glastac gel mixture with the genuine  Bullseye’s Glastac Gel I can at least tell you that I’ve had good results with the homemade substitute (with or without adding alcohol).

The homemade mixture still works as a weak glue. The improvement is that it no longer seems to cause little glass pieces to slide and shift as the glue dries. Other advantages are that it’s quick, easy and cheap to produce in small quantities and you don’t need to find more space for yet another bottle of glue.

If you find your homemade Glastac gel mixture works well you might consider buying some of the real Glastac Gel. At the worst it’s going to be no better. At best it’ll be even better.

Shelf Life

I found that leaving a small open pot of my homemade Glastac Gel substitute lying around for several weeks resulted in an “infection”. The feint tint of green near the surface leads me to suspect the beginnings of algal growth. Maybe I’ve discovered a new balanced diet for bugs. Hmm.

But all is not lost. Simply make up your homemade Glastac gel mixture in small quantities when you need some.

This does not mean you have to make up the CMC gel in small quantities. There is a shortcut. You may recall that I’ve already mentioned in Freeze Your Frits that your CMC gloop will freeze successfully. Store your excess in the freezer and make use of it a little at a time.


That’s all folks.

Posted in CMC, Experiment, Glastac, Tylo | Tagged , , , | 3 Comments

Shake Your Globs

If my early chattering about making globs from scraps of ordinary stained glass in Recycling Scraps of Stained Glass and with fusing glass at Waste Not Want Not have inspired you to make your own then maybe today’s blog will be of some interest. But only if you also do copper-foiled “Tiffany” style work.

Reducing waste and saving the planet is a good ethic, but what’s the point if you don’t make use of them?

I previously mentioned that kids enjoy collecting the recycled glass globs and that sometimes they can be used for pieces of jewellery too. Also, if you live in the land of deliberate bad spellers you might consider making jewelry with them instead.

Today’s theme is all about making use of recycled globs in your copper-foiled “Tiffany” style work.

Grind Before Foiling

Wrapping copper foil around a glob is a rather fiddly process. Not only is it a curved surface but it’s also rather smooth and slippery. The simple answer to this problem is to grind the edges of the globs so that you have a roughened surface against which the copper foil sticks more easily. Grinding can also be used to subtly re-shape a glob that has a defective or irregular shape.

Once you have wrapped the globs with copper foil you’ll want to burnish the copper foil and make the globs ready for soldering. Use your fingers to gently push-in the upper and lower edges of the copper foil but do not waste too much time on this. All that you need to achieve is a crinkly edge that needs the burnishing “finished off” by a method that is less fiddly and more efficient than using a fid or Allnova tool.

Burnishing the Foil

A simple and effective way to complete the burnishing process is to put your foiled globs into a jar with some un-foiled globs, put the lid on the jar, then shake until the burnishing process is complete. This trick is something I read on a forum years ago. So long ago that I don’t recall where or when. There’s no credit due to me for this burnishing method but I can at least recommend it.

dscf3492-globs-and-jarOn the right you’ll see a picture of a “half pound” jar, some un-foiled globs and some foiled globs. Notice the relative quantities being used. Notice that the foiled-globs still have crinkly edges to their copper foiling.

The number of un-foiled globs to use is not critical. It partly depends on the size of the jar just as it depends on how many foiled-globs are to be burnished. Too many globs in the jar means there’s not enough space for the globs to do their burnishing task. Too few globs in the jar means fewer impacts resulting in a slower burnishing process.

dscf3498-foiled-globsYou need to stop shaking as soon as the copper foil is burnished, otherwise the burnishing gets over-done and the copper foil starts to peel away from the globs. The picture on the right shows you the same foiled globs after burnishing. Good, eh?

This noisy task is enjoyed by children but do bear in mind that child labour (labor) is likely to result in over-shaken globs because they are more interested in the noise than the degree of burnishing. To mitigate this problem, reduce the number of un-foiled globs (or maybe eliminate them) so that the burnishing process is slower, thus extending their acceptable period of fun and enjoyment.

Using the Foiled Globs

You might think that there’s nothing more for me to say about how to use some copper-foiled glass. But you’d be wrong. If writing some more means there’s less time for housework then I’m not going to be deterred.

The privileges of childhood include the latitude to do stupid things like stuff small things up noses or in mouths. So, here’s an example of how I tend to use under-sized globs. Incidentally, it’s also a way by which I make use of the irregular shaped rectangles that we produce when squaring-off a wonky ends of newly purchased sheets of glass that were not accurately cut by the supplier.

dscf1719-glob-use-1In this picture you see a small area of a finished abstract piece of copper-foiled work, the design of which is motivated more by the use of scrap glass than intentional artistry. Of greater note in consequence of the theme of this posting is the use of foiled globs. Of incidental interest is the use aforementioned irregular-shaped strips of glass that tend to arise from “squaring-off”.

You can see that this particular example is not random. It may be a “sort-of rainbow” but in other pieces I arrange the globs such that they “sort-of flow” down through “sort-of cracks” between the irregular glass strips in the manner of “sort-of fractured rock”. Notice also that I’ve left a big hole (negative space) in the design. I also try to introduce excitement and interest by using different textures, differing opacity, slipping in a slice of agate or messing around with incomplete patination. Sometimes the best results come from not thinking too much!

dscf2414-glob-use-2My second example is what can be done when you have a huge excess of globs and can’t bear to throw them out. From the picture you’ll see one end of a “box of bubbles”. Just like the previous example I’m using both flat glass, foiled globs and leaving some holes. Incidentally, have you noticed that I chose a Wissmach hammered green border glass to reinforce the “blobby” nature of the interior of the panel?

There are two problems with this kind of panel. The first is that it can use up an awful lot of lead solder and the panels can get very heavy as a consequence. The second is that it’s very time consuming to make. So don’t make these panels too large and don’t expect to recover the real cost of making them if you intend to sell them!

My final comments relate to the technical matter of soldering thick globs into a panel made with thinner glass. You will no doubt realise that the sheet glass will be about 3mm thick but the globs might be 6mm. So, the globs will tend to “stick out” at the front.

If you want your globs to “stick out” only on the front of the panel then simply lay out the pieces front-side uppermost and get soldering without further ado. As an alternative you might try using thick card scraps underneath the plain glass pieces which then allows the globs to “sink” backwards into a more balanced and less proud form.

Concluding Remarks

So, there you have it. A couple more ways to save the planet by making use of recycled glass globs and a simple but effective way to burnish the copper foil onto globs.

A mercifully short blog and not one hint of maths or science. Aren’t you the lucky ones?!

Happy shaking and a happy (though belated) New Year.

Posted in Copper-foiled, Recycling | Tagged , | Leave a comment

Make Your Own Glassline Paper

Today’s chatter is for glass fusers and is about Glassline Paper. I’ll discuss how and why you might make your own, either because Glassline don’t produce exactly what you want or because you have the time and inclination to make a relatively inexpensive equivalent.

I don’t think I’ve inflicted mathematics onto you in previous blogs so now’s my chance. I hope to show you that mathematics (and the scientific method) can sometimes be useful, even when you’re not a mathematician or scientist.

Some Background

If you’re not familiar with Glassline products then a visit here will put you in the picture. Today we’re interested in the Glassline Paper and Glassline Pen products. I don’t often use them myself but there are times when they’re useful.

dscf3548-glassline-paper-examplesGlassline papers are available in a variety of colours, patterns, textures and sizes. Here’s a picture of a small selection of examples. You’ll find more examples at Glassline’s online shop here and summarised here in a single page. Both links contain information about how to use the Glassline papers.

As noted in those two links, Glassline Pens can be used to draw directly on Glassline Paper and I’ll come back to this little fact later when I talk about making your own papers. You can see a colour chart here and you will see the variety of standard colours is not large – but you can mix the colours if you wish.

Something worth mentioning for the benefit of novices is that Glassline Pens aren’t pens. They’re flattish bottles of coloured materials that can be fired and you can buy “stick-on” tips so that the bottles can be used as “squirty pens”. As is my habit, I refer you to the Manufacturer Safety Data Sheet (MSDS) page to find out what materials produce which colour and the all-important advice about how to safely use them. Potters amongst you will notice similarities with materials used in glazes.

dscf3554-glassline-pen-examplesThe picture opposite shows you a couple of example Glassline Pen bottles. Although you can also use a paint brush, an airbrush or whatever else takes your fancy, today we’re only interested in these Glassline Pens in one context – as the colourant for Glassline Papers.

Incidentally, Glassline only quote temperatures in Fahrenheit. For future reference, 1500°F is about 816°C and 1000°F is 538°C and you shouldn’t worry if you want to round off the numbers.

Now that you’re familiar with Glassline Pens and Glassline Papers, we’re ready to continue

An Accidental Discovery

It is quite some time since I discovered you can put Bullseye thinfire paper between layers of glass. I don’t think I ever remembered to mention this in past blogs so I now apologise and hint that this turns out to be part of what lies behind today’s discussion.

More recently I decided to buy a few Glassline Pens and a few small packs of Glassline Papers so that I could experiment with them. Until recently most of the packs of Glassline Paper remained unopened as I rarely find a use for them and have only spent a little time experimenting with them.

dscf3560-glassline-paper-logoOne of the packs of Glassline Paper I opened last week came with a surprise discovery. I noticed that the obverse (back) of the papers had the familiar logo and markings of Bullseye Thinfire paper. Previous papers did not have the Bullseye Thinfire markings. The picture opposite shows what I mean. Three sheets out of twelve identifying their origin doesn’t sound random to me so I was left wondering if Glassline didn’t intend to  reveal what their papers were made from. This is something we will test statistically in the next section.

A final realisation was that the Glassline Paper is coloured with what looks like and what feels like Glassline Pen colourants. This is hardly surprising when you remember that Glassline tell us that we can use Glassline Pens on Glassline Paper.

Mathematics is Fun

If the papers being used at the Glassline factory were unpacked and stacked randomly then we might expect half to be plain-side up and half plain-side down. If Glassline are trying to hide the fact that they use Bullseye Thinfire paper, in an attempt to obscure how their products are made, we’d expect Glassline to deliberately stack their Thinfire paper the same way so that the plain side ends up on the backs of their Glassline Paper, covering the Bullseye logo and markings with the colourants.

I have 12 sheets of Glassline Paper so would expect to see the Bullseye logo at the back of about 6 sheets if Glassline doesn’t care which way up they use the Thinfire paper. As already mentioned, I observed just 3 out of 12 having the logo on the back. If this is deliberate bias then it would be interesting to find out more and the Chi-squared test is how we find out.

For our statistical test we need to confirm (or reject) our “null hypothesis” that 3 out of 12 is statistically no different to 6 out of 12.

If that sounds daft to you, ask yourself these next two questions. Ask yourself “how many children of the same gender can a family have before we decide something weird has been happening” and ask yourself “how many times you can flip a coin and get the same result without getting worried that there’s something wrong with your coin”.

But I digress…

We start our Chi-squared test with some calculations based on observed (O) and expected (E) results. We have 12 samples, 3 of which have a logo on the back…

Paper Side         O         E          O-E     (O-E)2  (O-E)2/E

Back is plain      9          6          3          9          1.5

Back has logo   3          6          -3         9          1.5

We add up the two numbers at the right to get 3.0 and this is our Chi-squared value.

We now need to think about “degrees of freedom” because laying a sheet of paper (or flipping a coin) involves the freedom to do something that causes something to happen.

Should we decide to lay a sheet of Thinfire with the plain side upwards then we automatically know that the only other possibility is to have had the plain side downwards. Notice that we had two possible options and that choosing one of them automatically determines what the eliminated alternative was. So, two options gives us just one “degree of freedom” to choose. Therefore 1 is the degree of freedom we need for our Chi-squared test.

Looking at a Chi-squared table in the row for 1 degree of freedom we find 3.0 is a Chi-squared value that lies somewhere between the columns headed with 0.10 and 0.05. These two column headings are upper and lower bounds on the probability we’re looking for. These numbers can be represented in more familiar ways. Instead of 0.10 you could say 10% or 1 in 10. For 0.05 you could say 5% or 1 in 20.

Therefore, in human-speak, the 0.10 and 0.05 mean that 3 out of 12 sheets of Thinfire paper with their plain side upwards will happen somewhere between 10% and 5% of the time when we do our “sampling”. These are quite large probabilities which means our null hypothesis (that there is no difference) is probable. The corollary is that our original hypothesis is not probable. If our original hypothesis is not probable then Glassline aren’t trying to hide the fact they’re using Bullseye Thinfire paper and are therefore not actively using the Thinfire paper one way or the other.

Therefore, based on my small sample of 12 pieces of Glassline Paper, 3 out of 12 is no different than 6 out of 12. The same would apply to 9 out of 12.

If the whole concept of 3 out of 12, or 9 out of 12, being no different than 6 out of 12 has your intrigued or stunned, I challenge you to analyse some of the statistics behind advertising claims you’ll see on TV or the statistics being quoted by governments or other official bodies. Often you’ll discover the claims are being made on the basis of customer preferences, responses or equivalent measures that are not statistically valid. Knowledge is power.

If all that babble left you realising you’ve forgotten all your mathematics then here is where you can revise your Chi-squared test. It’s also where you can find a Chi-squared value table.

Making Your Own

And at long last we come to the most important part of my chatter – telling you what Glassline Paper is made of and how you might make your own equivalent papers.

All you need to make your own is Bullseye Thinfire paper, some Glassline Pens and a method of production.

There are many methods by which you can apply the colour to the papers. Some of them are mentioned by Glassline. You might use a paintbrush, sponge pad, an airbrush or whatever else comes to mind. Sometimes you may wish to add water to make a thinner mixture, especially when you want to use an airbrush or want to produce a paler tint.

Remember also that Glassline tell us that we can use Glassline Pens to decorate their Glassline Papers.

dscf3561-glassline-overspillAlthough Glassline Paper tends to have colouring on one side, you will notice in the picture opposite that some papers have overspill on the reverse side.  I don’t suppose Glassline care about this overspill beyond recognising it means they’re using more colourant than they’d like to. For us, it means we have to buy papers that are neither single-sided nor double-sided. But bluntly, the backs are an untidy mess. I don’t like mess and it detracts from the quality of what we try to achieve with out work.

dscf3551-glassline-heart-2dscf3551-glassline-heart-1In these two pictures, on the left and right, you can see that it is possible to have one colour on one side and a different colour on the reverse. It may be a shabby example with sparse artistic merit but it does show us that there is no colour bleed from one side to the other other than my messy experimental workmanship.

dscf3549-glassline-paper-diyThe picture you now see offers a few examples that show we’re not limited to what Glassline have in their Glassline Paper product range. The grey-looking rectangle will fire to double-sided black. The narrow strip at the top has different colours on each side. The two examples on the right are single-sided and have two colours. The remaining example at the lower left is a single colour of brushed stippling.

And finally, do remember that when the thinfire paper has been fired, the Bullseye logo and associated markings will disappear.

I think you get the idea and hope these example inspire you to do your own experiments.

Thinking About Economics

It is worth considering the relative costs of buying ready-made Glassline Paper against making our own. What follows is a quick analysis that in turn will lead to some simple conclusions. If you’ve had your fill of mathematics then just skim read this section!

To begin with we need to know how much it costs to buy ready-made Glassline Paper. For those of you in the USA I offer you the Suede Glassline 5″x5″ Stone Paper kit as an example. For this product three sheets of 5 x 5inch costs $15.45. This equates to about $0.0319 per square cm.

By contrast, in the UK we might expect to pay £8.91 or thereabouts for a mix of 15 sheets of 6.5 x 6.5cm at Warm Glass UK. This is a similar quantity and equates to about £0.01406 per square cm.

We now need to compare this with the costs to make your own version of Glassline Paper.

Bullseye Thinfire paper costs vary depending on how much you buy and where you buy it. For the purposes of our calculations let’s take £19.47 for 10 sheets of 52x52cm quoted by Warm Glass UK. This turns out to be about £0.000720 per square cm. With modest bulk buying the cost of the Thinfire paper turns out to be a negligible cost when heading down the DIY route.

Glassline Pens cost around £7.25 or thereabouts from Warm Glass UK when bought in 2 ounce bottles. That’s about 56 grams for those of you who stopped using Avoirdupois units decades ago. Translating this mass into how much gets used per square centimetre is rather tricky as it depends on what we’re doing and how much water is in the mixture. A light wash of colour is going to use a lot less than a thick coating. All we know is that the colourant is costing us £0.1286 per gram used.

Let’s look at the problem in a different way instead. If we can limit our use of the Glassline colourant to less than £0.01334 per square centimetre we’re on a winning streak if we’re out to save money. We know this because we have calculated how much the finished Glassline Paper and raw Bullseye Thinfire papers cost per square centimetre.

But how much can we squirt out of a Glassline Pen before it costs us £0.01334? A quick calculation tells us it will be about 0.1037 grams per square centimetre. A tenth of a gram is a tiny amount, nothing more than a blob on the end of a skinny wooden coffee stirrer. However, even a tenth of a gram is enough to cover a couple of square centimetres of Bullseye thinfire paper with a heavy application and considerably more for a light coating.

But let’s not forget that we’re likely to find ourselves with mucky paintbrushes, palettes, airbrush equipment or whatever else we’ve been using as tools. Some of what was in our Glassline Pen will go down the drain as waste. Waste costs money too.

Practical Conclusions

If you have painterly skills then making your own versions of Glassline Papers is a viable proposition in many situations. Sometimes the cost to buy ready-made outweighs the time and effort needed to produce your own equivalent versions. Sometimes the uniqueness of what you make makes simple cost comparisons pointless. It’s a matter of judgement.

A generally applicable comment is to buy cheaply and minimise waste. This is common sense, but a failure to do this can negate your attempts to save money if that’s what you’re aiming for.

Heavy coatings of colourant laid on Bullseye Thinfire paper ought to be a financially viable alternative to buying ready-made Glassline papers but three factors should be borne in mind. If the thinfire paper is being purchased expensively in small quantities and if the results of the DIY activity result in a lot of waste colourant it is easily possible to make papers that are more expensive than could be purchased ready-made. Also realise that the time you take to make such papers adds to their cost.

In extreme contrast to heavy coatings, an airbrush can be used to disperse small quantities of watered-down colourant over a large area as speckles. This method ought to be the least costly because it uses the least quantity of colourant. Do remember that airbrushing speckles will only be financially viable if you already own an airbrush.

Related to speckled effects would be brushed effects, drawn effects or sponged effects, especially when watered-down colourants are being used. Again we should expect relatively low costs that are viable compared to ready-made papers.

Some of the Glassline papers will be harder to replicate and will use a lot of colourant. Examples of the crinkled, granite and sandstone papers where Glassline use two colours and/or the thinfire paper that has been “crumpled” and flattened-out before applying the colourants. Unless there is a compelling reason to make your own I reckon it’s not worth the trouble to make these at yourself, other than as experiments for the learning experience. Not only will it be a time-consuming task but the amount of colourant and waste colourant are likely to make it more expensive than ready-made papers.

A final conclusion is that we now realise that Glassline papers with overspill on their backs can be “finished off” to make them double-sided rather than “single-sided with mess on the back”. It may not matter to Glassline, but I try to consider how things look from the back of what I make.

In the final analysis, the most compelling case for producing your own papers is when you want to colour both sides of the thinfire paper and when you require colours or patterning that can not be obtained ready-made from Glassline.

Posted in Experiment, Glassline Paper, Glassline Pen, Inclusions, Money-saving ideas | Tagged , , , , , , , | 4 Comments

Secrets of the Microwave Kiln

I’ve just bought my third Hot Pot Maxi microwave kiln. But, why buy yet another “toy” kiln when I already have a “proper” glass kiln of a distinctly robust and modern design?

I hope to answer that question by talking about the distinctive nature of firing glass in a microwave kiln, a little about the economics of using them, and a little about how they work and how they deteriorate.

I think I need to do all of this because I don’t see anyone else talking much about it.

Experiences With a Microwave Kiln

I still use a microwave kiln because I can melt a small arrangement of glass and have it back out and in my hands, fused and shiny, within about two hours. My “proper” kiln makes me wait a whole day (and night). So, speed and convenience is one reason.

The barely-controllable ferocious heating in a microwave kiln results in a greater risk of glass cracking at it heats up and the lack of processing temperature control means it’s not uncommon to find a mutant distorted blob of glass is the unexpected result of a firing. And of course the small firing chamber means we don’t get to make anything larger than a brooch or pendant. Sometimes this is not a problem.

The down-side of the almost uncontrollable heating, as I’ve just mentioned, is that the shape and form of the resulting glass masterpiece is rather unpredictable. This becomes a particular problem when the microwave kiln gets older and heats less evenly. I’ll be coming back to the “getting older” aspect of microwave kilns later as it seems to be a widely neglected topic!

Another characteristic of microwave kilns is the incredibly rapid cooling inside the microwave kiln. It has scant regard for “proper annealing”. You might think that this must lead to problems but in truth it very rarely does.

We are repeatedly told that it is important to properly anneal our work. From this we might suppose that the rapid cooling in a microwave kiln without “proper annealing” might cause us significant problems. In truth I find that breakages caused by poor annealing are very rare. If this is a surprise to you then consider the size of items being produced and realise there’s only so much stress and strain that can be built up and “stored” in such a small piece of glass. This is particularly the case for simple shapes like a blob of glass, a little decorated tile or a simple pendant – in other words, exactly the kinds of things that you’d use a microwave kiln for.

You can, of course, pop your microwave kiln masterpieces into a “proper” kiln to “properly anneal” them though we can take paranoia too far sometimes.

Another aspect of the rapid heating and cooling in a microwave kiln that I have not seen mentioned anywhere relates to devitrification. With a microwave kiln the processing time is so short that glass that is susceptible to devitrification rarely has time to devitrify. A practical consequence is that I am able to reliably produce recycle my otherwise unusable scraps of “ordinary” non-fusing glass into blobs with little risk of devitrification. You can see real examples in my Recycling Scraps of Stained Glass blog and you should bear in mind that every single glob you see in the picture is not fusing glass. For the lazy amongst you, and because it’s colourful, I’ll re-post the picture from that blog:

DSCF1857 Recycled Glass Globs

And here’s and interesting example that proves the opposite situation from my last blog. This little wonderous spiky blob of glass devitrified before it melted completely:

DSCF3010 Spiky Devit

The big surprise is that my “proper” kiln fails to produce shiny globs with “ordinary” non-fusing glass. Devitrification is always a problem. Processing time is important when dealing with glass that was not designed to be re-fired.

In other experiments, using a “proper” kiln, I find that most kinds of “ordinary” non-fusing glass can barely cope with slumping without devitrifying at least to some degree. Someday I’ll do a blog about this but I’ve not finished messing about yet!

Reasons to Use a Microwave Kiln

A consequence of the foregoing chatter is that I continue to use a microwave kiln in four very particular situations:

  1. I can quickly and cheaply perform a simple glass-related experiment in a microwave kiln. Firing-up a big kiln and waiting a whole day to find out what happened can be too long to wait sometimes.
  2. Children visiting for a “smashing time” can arrive in the morning to make something small and simple in a microwave kiln then take it home that same afternoon. While they wait for the microwave kiln too cool down they can also make something bigger and more “special” that later will go into the big kiln. Immediacy is important for kids, as is the excitement of seeing seething red-hot glass when they “peek”.
  3. I can recycle scraps of non-fusing glass into blobs without devitrification problems and in turn it means I throw very little waste glass away.
  4. I can quickly make small quantities of frit balls (and other similar little things) when I run out of them which means I don’t have to suspend my project work for a long time. That they’re badly annealed doesn’t matter here because they will be fired again!

You may be surprised to learn that point (3) is what my microwave kiln gets used for most of the time. Let me explain…

No matter how hard we try to make use of smaller pieces of glass we end up with small scraps that are unusable. Where possible unusable scraps get melted into globs. It makes environmental sense through I doubt the time and effort to make them is commercially viable.

Some of the smaller globs (under 6 grams) I use in my own copper-foiled work or give away to other crafters when we meet at events. They might end up as a glass highlight in a wooden decoration for example.

Larger globs (typically 6-10 grams) are supposed to be sold though I tend to give away most of them. My rule is simple – kids who show an interest in my work can have one free but horrible kids have to pay for them. There has to be a reward for being “nice”.

Microwave Kilns Deteriorate

I’ve already mentioned that I’m now on my third Hot Pot Maxi microwave kiln. What happened to the other two?

As battered and bruised old-timers the old microwave kilns have been retired. They now live in landfill. The blunt truth is that they’re fragile, get damaged easily and really do get old and tired.

I should now explain how a microwave kiln works (in brief) and then pull-in information to explain how and why they deteriorate and get old.

The body of a microwave kiln is made of a light and brittle ceramic material. Considering how light and thin the ceramic material is, it performs remarkably well as a thermal insulator.

With a new microwave kiln we can expect the grey heating material to heat up reasonably evenly. The relatively small degree of uneven heating will be caused by subtle differences in the mixture of materials and their thickness. With time the degree of uneven heating gets worse for reasons that follow…

Repetitive heating and cooling causes repetitive expansion and contraction which will result in hairline cracks. The brittle nature of the ceramic material (and the inside coating) of a microwave kiln means it starts rather soon and gets progressively worse the more you use the microwave kiln.

Exactly where the hairline cracks appear depends on the unavoidable “defects” of manufacture and some basic physics. That the cracks always seem to run from top to bottom is purely down to the combination of geometry and coefficients of expansion – the inside gets hottest so wants to expand proportionately more than the outside. The reverse happens when cooling. This difference causes stresses and strains which result in hairline cracks appearing. So, don’t be unduly concerned by hairline cracks because they’re a natural consequence of the heating and cooling and the materials being used.

We now need to remember some high school physics. Do you remember that heat can be transferred by any combination of conduction, convection or radiation?

The hairline cracks will cause uneven heating because areas that heat up fastest can not conduct some of their heat to cooler areas because of the barrier caused by the cracks. So, any minor differences in one area heating up faster than another due to original manufacturing “defects” is made more pronounced when hairline cracks come into play. As the size of the firing chamber is so small we can assume there is no heat transfer by convection. There will however be some heat transfer by radiation because that’s what we’re using to heat up the glass in the firing chamber.

So, uneven heating becomes an unavoidable and noticeable problem once the microwave kiln starts to develop hairline cracks. This in turn adds to the unpredictability of what you can produce in a microwave kiln. A partial answer to this uneven heating is to pause the firing mid-way, have a peek, rotate the lid by half a turn, then continue to the firing. With practise and good timing this can almost negate the effects of uneven heating.

Glass slippage is another problem because. It is very easy to accidentally nudge the lid of the microwave kiln and cause the glass pieces inside to slip. A microwave oven platen that rotates badly (wobbling or shuddering) can also cause glass to slip. Heating too rapidly may cause glass to crack and move, so is another form of slipping. Any of these (and other) mishaps may result in hot glass “gluing” itself onto the base or the sides of the microwave kiln. You can also achieve the same effect by over-cooking the glass such that it becomes very fluid and “runs” to the side of the kiln to glue the top and base together.  Yes folks, I confess. I’ve experienced all these mishaps.

The trouble with glass fused onto the ceramic material is that you will find yourself gouging a big hole into the base or sides of the microwave kiln in your attempt to remove the glass. It is rarely possible to remove the glass without damaging the ceramic material, even if you have use kiln wash to protect the kiln base. Such mishaps tend to shorten the life of a microwave kiln, either because you find yourself with a kiln base that resembles the aftermath of World War I trench warfare, or sides where big chunks of the grey heating material are missing.

Using kiln wash and fibre paper can help deal with some of the problems some of the time but in my experience they will only reduce the rate of kiln destruction!

Another aspect of the deterioration relates to the heating ability of the dull grey gritty substance on the inner surface of the microwave kiln’s lid. It’s the heating element. The dull grey gritty substance is something I’ll talk about in more detail at the end of this blog so for the moment just accept that it is chosen for its ability to absorb microwave energy and re-emit that energy as heat. In other words, a microwave kiln works because of a peculiar characteristic of the grey material.

I am not sure why, but the effectiveness of the grey “heating” material seem to deteriorate over time, partly because of minor mechanical defects such as hairline cracks, but also because it seems to take longer and longer to heat up as the kiln is used more and more. This is something I noticed with my first microwave kiln but I hadn’t been keeping any records.

The fact it takes longer and longer for the microwave kiln to heat up with age implies there is some form of chemical deterioration in the “heating element” part of the microwave kiln. Anything that’s hot and in air tends to get oxidised as a matter of routine. This is perhaps most familiar to you if you’ve ever put some lovely salmon-pink shiny copper elements in your kiln-fired work and was disappointed to discover they came our red, purple or even black as heat and oxygen progressively turned the copper to copper oxide. This is what heat and oxygen routinely do to most things around us. This is what I suspect is happening to the “grey stuff” in the microwave kiln. But I suspect there are two other possibilties.

One of the alternative possibilities is that metals in coloured glass are “firing off” and reacting with the heating element. The other possibility is that the mixture of materials in the heating element react with each other causing chemical changes.

Whatever the cause, the effect is that the heating element becomes less susceptible to microwave energy so is not able to re-emit heat so effectively.

Firing History

My first microwave kiln told me that there was deterioration. So, for my second microwave kiln, I kept a record of each firing. Not much more than the date, what kind of task and how long it was “cooked” in the microwave. What you see in the graph below is the result of my nerdy record-keeping. Have a look at the graph then I’ll explain what it all means.


The graph shows that my second microwave kiln didn’t quite make it to 300 firings before I felt it was time to throw it away. The exact number of times was 283.

You can also see from the graph that the jagged curve runs from the lower left (the first few firings) to the upper right (the end-of-life firings). Notice also that the curve is steeply upwards on the left and goes shallow on the right. This curve tells us that a new microwave kiln is much quicker than an old one and that the super-duper performance of a new microwave kiln doesn’t last long.

Notice that I’ve scaled the processing time so that 100% represents how quick the new kiln was. This means that when I threw it away it was taking almost twice as long to do exactly the same job – over 180% of the original firing times. Notice also that the graph shows us that the rate of deterioration slows down and seems to be levelling out at around 180%.

There are consequences for this “deterioration”. One is that it takes more time and energy with an older microwave kiln when compared to a new one. The other is that there’s no point in relying on detailed accurate firing records with a microwave kiln because its behaviour changes over time.

I’ll now reinforce that last paragraph in a different way. If you use a firing time from an old microwave kiln to guide to what you should do with a new microwave kiln you will likely “double blast” your glass. It will be “double processed” and you may end up producing an very runny pool of molten glass. And runny molten glass flows rather well if a surface is not exactly level. This is how I managed to “glue” the inside of the lid of a microwave kiln onto its base using molten glass. Don’t be as stupid as I can be. Consider yourself warned!

Now that we have some evidence about how microwave kilns deteriorate, and why, lets look at the economics of using a microwave kiln.

Microwave Kiln Running Costs

There are different brands of microwave kiln and some brands come in different sizes. The kind I’m using has a firing chamber that is about 10cm in diameter and cost about 50 GBP. Knowing that your 50 pound investment will deteriorate and may be ready for landfill after about 250-300 firings is something to think about. So is the ever increasing cost of the electricity, the kiln wash, fibre paper, currency exchange rates etc.

So, how much does it really cost to fire-up a microwave kiln? Lets find out…

I’ve already mentioned 50 pounds Sterling (notice it’s “Pounds Sterling”, not “English Pounds”) as the purchase price of my new microwave kiln and that I got 283 firings out of my second microwave kiln. So, that’s about 17.6 pence per firing due to the kiln cost.

But electricity also costs money. I am using an old 650W microwave oven. The 650W measure is the microwave output, not the electricity consumed. From the technical information at the back of the microwave’s manual I see it consumes 1.1kW per hour. So that’s about 60% efficient. My electricity costs around 16 pence per kWh and I’ve factored-in a proportion of the standing charge. We end up with just a few pence of electricity per firing which I can now plot on a graph.


I see that the cost starts somewhere between 3 or 4 pence, quickly rises to nearly 5 pence, then slowly drifts upwards to a little over 6 pence per firing. If you compare this graph with the previous one you’ll see exactly the same shape but a different Y-axis scale. This is because we’re doing nothing more complicated by converting a Y-axis in units of time into units of pence by multiplying by a constant value. For full marks in a mathematics exam I should have perhaps chosen a Y-axis starting at 3p rather than zero to make better use of the space.

Other Running Costs

There are other running costs that were not included in the previous graph. We tend to use some kiln wash to protect the base of the microwave kiln. A tiny fraction of a penny per firing for kiln wash is negligible compared to the cost of your time and the other costs associated with running a microwave kiln.

You, like me, might also use Bullseye’s thinfire paper between the glass and the kiln surface. It’s expensive and it can’t usually be used more than once. But how expensive is it?

If you’re lazy you’ll buy ready-cut 10cm squares at around 11 pence per firing, such as from here at Glass Studio Supplies in the UK but if you compare the price for buying 100 big sheets, such as from here from Warm Glass in the UK, you find you could instead be paying around 6 pence for the same amount of thinfire paper. All it takes is the will to buy in bulk, a pair of scissors and a few minutes of your time.

And finally, we need to remember to allocate a portion of the cost of buying the microwave kiln to each firing as well as the electricity cost, both of which were calculated in the previous section.

Overall Running Costs

My second microwave kiln tells me to expect a lifetime of about 250-300 firings, or maybe more if I treat the microwave kiln with more respect and care. As most of my use of a microwave kiln is to produce circular blobs of glass, we’re talking “full-fuse-plus”. We might therefore reasonably expect a longer life for the kiln with profile fused work.

Record-keeping may be boring and nerdy but it clearly has its uses. I now know the lifespan for my second microwave kiln and how it has behaved from new until the time I threw it away. Combining all the information at current (2016) UK prices tells me that the total per firing will be somewhere in the region of 25 to 35 pence, depending on how old the microwave kiln is, the kind of work being done, and whether or not I am prepared to buy raw materials in bulk.

You might like to think about how costly it is to fire-up your “big kiln”. The same ideas and methods apply, but the numbers will be bigger.

How Microwave Kilns Work

If you’ve got this far and have an urge to find out more about how microwave kilns work, and would also like to know how you can make your own, you’re in luck. I’ve gathered together a few links below which I’ll pad out with some commentary.

When you hunt around the Internet you’ll maybe find some misleading information about “the grey stuff” in a microwave kiln. The grey material is not granite, nor is it graphite. It is a mixture of silicon carbide and sodium silicate. Notice I say silicon and not silicone. Silicon is a shiny silvery metal. Silicone is a kind of plastic used for waterproofing products, breast implants and more besides. Silicon and silicone are not the same things.

You will be familiar with silicon carbide as an abrasive if you’ve ever tumbled rocks and minerals. You will also be familiar with sodium silicate though it’s unlikely that you realise it. Both are inexpensive chemicals that you can buy on eBay and I’ll give you a couple of links later that tell you more about both of them.

Once upon a time I found a reference to both these materials when I was reading something about LVR Products’ Micro-Kiln EZ-5 and Micro-Kiln No 9. I made a note that in their parts list it said there was a ‘Repair Solution Set’ which consisted of Silicon carbide (solution A), Sodium silicate (solution B) and a Brush. I forgot to make a note of the URL and I can’t find with Google any more, so I’m sorry I can’t give you a link to this evidence. But not to worry. I have more sources of information, as you will see later, that should reassure you I’m not talking out of my backside.

Silicon carbide is used as the heating element because it has the interesting property of absorbing microwaves and re-emitting the energy as heat. You can find out more about this grey “heating” chemical at Wikipedia’s entry for Silicon Carbide (especially in the Heating Elements section). You will also find silicon carbide mentioned in some of the links listed below.

To “glue” the silicon carbide to the microwave kiln lid requires a binding agent and although there are several possibilities, you will you find that the commercial repair kits seem to use sodium silicate. Find out more about this “binding” chemical at Wikipedia under Sodium Silicate (especially in the Refactory Use section).

Over at Paragon you will see repair instruction that mention a silicon carbide layer. Actually, this is a very useful little instruction manual for any microwave kiln user, not just the Paragon MagicFuse microwave kiln.

You can get a really good insight into how microwave kilns are made by watching a YouTube video called How to make a microwave kiln (Furnace) from scratch for £5 but the link is now private and inaccessible to us mere mortals. The audio is not good but it is worth the struggle. Not only will you see a microwave kiln being made but you discover silicon carbide is just one of many “susceptor” chemicals that can be used as a heating product and that there are different binders, not just sodium silicate. Also interesting in the narrative is an explanation of how the same heating method is used to cook microwave chips.

With the “old” link now inaccessible I suggest you watch the YouTube video called Diy Microwave Kiln | Melt Glass in the Microwave as well as another called How to make a Microwave Kiln – Easy and Cheap DIY Glass Fusing & Melting for a less comprehensive insight. If nothing else they confirm the use of silicon carbide and sodium silicate as appropriate materials.

You can find out more information about microwave absorbers here though in a completely different context.

If this isn’t enough for you then there is an old technical reference about “self heating” ceramic crucibles for microwave melting of metals and nuclear waste glass  at the Office of Scientific and Technology Information in the USA which is not as irrelevant as you might initially suspect. Vitrification has for many years been considered as a “safe” method of disposal for nuclear waste materials.

For the fearless amongst you, I have found some rather technical references. I can promise you an especially dreary read with this patent. If it is too much for you, I suggest try the readable article here because they’re both about the same thing.

Are We Being Ripped-Off?

And finally, we should give some thought to whether microwave kilns are good value or not.  The same applies to repair kits that you might encounter.

For almost the cost of buying a replacement microwave kiln you can buy a microwave kiln repair kit. One example is here. I am always suspicious of spare parts and repair kits that cost almost as much as the original item.

If you have a look in eBay (or elsewhere) you’ll discover just how cheap silicon carbide and sodium silicate really are. This should make you wonder why there’s such a big difference between the price of these raw materials and the price of a commercial kit or a microwave kiln.

If you understand the instruction in the YouTube video I mentioned in the previous section you’ll begin to understand that 50 GBP is ten times the cost of making your own. Again, this should make you wonder why there’s such a big difference between the price of the raw materials and the price of a commercial microwave kiln.

Yes folks. Information is power. The power to exploit. And now you know their secrets they can’t exploit you so easily. But you can exploit what you know. You too can make a microwave kiln. You too can buy the materials you need to make your own repair kit.

If you enjoy making things and you don’t have a microwave kiln then making one is surely a candidate for the top of your “Things to Make” list.

Bye for now. Tomorrow I’m going to make some rainbows. How about you?

Posted in Devitrification, kiln schedule, Melting Glass, Microwave kiln, temperature curve | Tagged , , , , , , | 30 Comments

Traditional Leaded Light Construction

It’s not often that I construct a leaded light but having done so recently I thought I should share some notes with you. They may help you as a newcomer or give you some new ideas if it’s an activity you’re already familiar with.

I really cannot claim to be an expert so you might have different opinions and ideas and might even think I’m doing it all wrong. Use your own judgement and decide for yourself. Sharing the information is what’s important from my perspective.

Rather that write this blog as a tutorial, for which there are several to be found online and in books, I will break down my notes into short sections that broadly follow the construction steps but I will not concern myself with step-by-step instructions. Sorry if you find this results in a blog that is a little incoherent at times.

Two Schools

There are two schools of thought about what to do once a cartoon has been produced. The difference lies in the method by which a cartoon is translated into a set of glass pieces ready to assemble.

Incidentally, I use the word “cartoon” for a drawing of an intended design. You might be more familiar with “pattern”. I think there’s a subtle difference that makes “cartoon” more appropriate but we can beg to differ on this little matter.

The first school of thought is that you must make a copy of your cartoon and use scissors on the copy to make little templates that represent each of the pieces of glass. I find this time consuming and fiddly so only use this method when I am using opalescent glass or dark colours that I cannot see though.

The second school of thought is to use the cartoon to directly score the glass directly over the original cartoon. This is a quicker method, lazy some might say, because it requires no copy to be made and there is no scissor work. This is what I tend to do if I am using glass that I can see through. I also prefer this method because and there are no fiddly bits of paper getting in the way of glass cutter wheel and no little pieces of paper to lose. One might suppose that parallax error might make this method slightly less accurate because of the distance between the cutting wheel and the cartoon lines but for leaded light work this does not tend to be a problem.

As already mentioned in passing, I still sometimes have to use the first method when working with a dark cathedral or opalescent glass. In this situation I mark-out a copy of the pattern for individual glass pieces using tracing paper, cut-out the tracing paper and use this as the template. I then use a waterproof marker pen, or a white wax pencil, around the edge of the template to mark-out the perimeter onto the glass. I don’t stick the paper onto the glass and attempt to score around it as I find the outcome is worse score lines.

Whichever method you use, it can be a good idea to number the pieces of glass to match the number you’ve added to the cartoon (and maybe template pieces) so that you don’t forget where they go and indeed which way up the pieces of glass should be used. This is particularly important when the design is complicated and has many pieces of glass that are similar but not exactly the same.

DSCF3325 CartoonSomething extra that I do with leaded light cartoons is to pencil-in lines that represent the boundaries between the glass and leads. Whilst doing this I also consider how the pieces of leading will affect visual appeal, construction strength, how it will be assembled and so forth. So, in addition to marking-out where there will be leads I also mark how those leads should be cut and jointed as a reminder for later. Look at the picture for a better understanding of what I mean.

The thick black lines on the cartoon will be explained in the next section.

Can you see I stopped bothering to mark out the cames and joints in the lower part of the panel because it was the “easy and obvious” part? I find that marking-out the cames and joints is more important for the complicated or intricate areas than elsewhere so I sometimes allow myself to be lazy in the less critical parts of the design.

If you leave these assembly and jointing considerations until the assembly phase of the construction and try to do it “on the fly”, your mind and your eyes will tend focus on the immediate task at hand – which is to say the current piece of glass and lead came. This means you will tend to neglect the “bigger picture” and often forget any thoughts you had about what to cut, where to joint and so forth.

Another dividend is then repaid when assembling the panel because you instantly see whether or not each piece of the lead work is being placed exactly in the correct position and is the expected shape. This in turn means construction problems are caught early and can be addressed immediately. You don’t have to wait until the panel has been fully assembled to realise that lots of subtle little errors have produced a wonky distorted panel that’s not quite the size it was meant to be.

Cutting the pieces of glass to the “right size” is important and the “right size” depends on the construction method and materials being used.

If you simply score along the cartoon pattern lines your will end up with glass pieces that are too large because no allowance has been made for the thickness of the lead between pieces of glass in a leaded light. A different allowance must also be made for the a double-thickness of copper foil (and a little solder) when using the copper-foiled method. So, the “right size” is a little smaller than the size on your nicely drawn cartoon drawing.

Commercially available pattern shears are available that will automatically cut on each side of the cartoon’s lines to help you with this task but I do not use them. One kind of shears is for copper-foiled work and the other is for leaded lights. The only difference between them is the amount of size-trimming that they perform. But there is a simpler method that is not only cheaper but is, at least in my opinion, more effective…

Look back at the previous picture and notice the thick black lines. Then read on…

Mark out all the glass boundary lines in your cartoon design with a felt tipped marker pen that produces lines about 2mm thick if it is going to be a leaded light. If you intend to use the copper-foiling method then a finer marker pen that produces lines no more than 1mm wide is appropriate.

You will then score along the edges of these marker pen lines, not the middles of them.

Thus, the thick marker-pen lines represent the channels inside your lead cames. Because 2mm is slightly more than the thickness of lead in the channel we can be sure the pieces of glass will not only fit but should rattle slightly.

The reason we should aim for slightly under-sizing the glass pieces is to ensure that the panel as a whole can be constructed exactly as the cartoon design intended, which is to say the final product will not contain distortions and can be made to exactly the correct dimensions. Although there will be some rattling of glass pieces around the constructed panel it will be entirely resolved by the waterproofing and strengthening stage of construction. But, there is a difference between being “a little too small” and “too small” and it depends on the width of the lead cames you are using. Wide leaves (flanges) of chunky cames means you’re allowed more latitude. Narrower cames demand more careful cutting!

And by the way, if you have the habit of using waterproof marker pens to mark-out the glass cutting lines then a smear of something like petroleum jelly (eg Vaseline) will help to stop the lines washing off when subsequently grinding. An alternative is wax pencils. A lazy third alternative is to place a sheet of clear acetate over the cartoon to protect it from water, then repetitively grind and check the piece of glass against the cartoon.

Obtaining and Storing Lead Cames

Lead cames are produced in straight lengths and that’s how you should try to obtain them. Avoid buying lead cames that have been coiled-up because it requires more effort to straighten them and increases the chances of physical damage. If this means you need to visit a stained glass supplies shop one per year rather than have it posted to you in coils then do so.

Once bought, give some thought to transporting and storing your lead cames straight and flat. Some possibilities are a long sturdy cardboard postal tube, a piece of plastic drainpipe or even a piece of plastic guttering. You glass supplier receives the lead cames in crates – maybe they are kindly folk and have one spare that you can have.

If you live in a damp environment, or your work area gets damp, try not to buy more lead came than you need as it will deteriorate through oxidation and become harder to solder. If you live and work in a nice dry environment then this is less of a problem so buying in greater bulk is more viable.

I have in the past been “donated” really old lead cames that had lain unused for many years. They had almost turned to black and were an absolute swine to solder and it was (in practical terms) impossible to “brighten” the leads where I intended to solder. So, if someone approaches you with a fist full of twisty mangled ancient lead cames, politely decline the offer even if they are free!

I should perhaps briefly describe some common forms of lead came, particularly for novice readers. What you choose comes down to artistic necessity, suitability and experience.

H-section cames are what you will mostly use so I will talk mostly about them. You will notice they have 5mm wide channels into which the glass pieces fit. The overhanging leaves (flanges) will keep the glass in place even before you’re waterproofed and strengthened your masterpiece.

But why not a 3mm channel for the glass we tend to use? The answer is easy. Think about the effect of surface patterns and the thickness variation of hand-blow glass. The extra 2mm is needed to accommodate such situations!

Another aspect of H-section cames is that the leaves “overhang” the glass by differing amounts. In this regard it is like choosing between thin or fat copper foil – part of the choice relates to the visual effect but there are also underlying practical consequences. A consequence of choosing H-section cames with wide leaves is that there is more latitude for error in the glass cutting and a stronger layout at the expense of a “chunky” appearance to the finished piece. Finer cames demand more accurate glass cutting just as using skinny copper foil only looks good if you cut the glass accurately.

H-section cames are available with “leaves” that are may have flat or curved outer surfaces, or both. In practise it doesn’t matter whether the leaves are flat or curved, and you will not really notice the difference except in one situation – accidentally mix them up in the same piece and it looks shabby with both flat and curved surfaces on the same side. I’ve accidentally done this in the past so trust me!

There is no reason why you cannot mix-and-match different types of H-section came in the same piece. For example, if your design contains a nice traditional stylised flower (not unusual!) you might choose a “fatter” came below to represent a stem for that flower.

U-section came and C-section came need special attention because their names are often confused. U-section came isn’t just C-section came turned on its side! They have different cross-sections but more to the point, they have very different purposes.

C-section came might have curved or squared-off outer profiles when viewed in cross-section and tend to be used to form a framing edge for a panel or inside a wooden frame (eg a cabinet door). Consequently they are often used for a standalone piece such as a suncatcher and sometimes have a narrow channel that is around 3mm rather than 5mm so be careful before your buy such cames. Incidentally, I hate the term “suncatcher” because they don’t catch the sun and they’re not necessarily hung in a window and it explains why I tend to use the word “panel” instead. But again we can agree to differ!

C Section Came UseU-section came is interesting. When you find some to look at, notice the heavy-duty curved outer profile in cross-section. The reason for such a sturdy curved profile is because U-section intended to be used as the upper edge of a large panel section that will have another panel section resting on top. To understand what I mean, think of a massive stained glass window in a church which has, by necessity been constructed in sections. Now look at my rubbish little diagram to understand how the H-came (in red) and C-came below (in blue) are being used. Over time the H-section presses down under the weight of the upper panel and the H-section’s leaves will splay and form a nice neat seal over the C-section curve below. Rainwater will remain outside and not be drawn into the panel. A simple solution to making a massive glass window panels waterproof wherever they meet. Our ancestors were not so primitive as we sometimes assume!

And finally, remember there are other forms of lead came for special situations. Some cames are for forming a right-angle joint. There are others designed to be the perimeter of a piece that makes it easier to mount into a frame. Visit your stained glass shop or look at a web site and ask what they are intended for. Nice people like to share their knowledge and experience.

Stretching Lead Came

Lead came needs to be stretched a little before use, not only to remove kinks but also to make the structural properties of the lead change. Somehow a stretched came seems to be a little stronger.

Stretching ought to be done only once per came, so to avoid confusion don’t stretch a came until you need it and store leftovers in a different place from un-stretched cames.

Two people holding each end of a length of lead came with pliers (or a similar tool) can perform the stretching. If there is nobody to help you then a lead vice will be needed and the vice must be screwed to a table top or clamped into a sturdy vice. Don’t attach the lead vice to your best table and don’t trap one end of the lead came into a door frame – these are both effective ways to damage woodwork!

How far to stretch the cames is a matter of judgement. What you are aiming for is the removal of kinks plus just a little more. Do not pull too hard or stretch too far as the lead will start to lose its strength and become softer. Worse still is if you pull too hard and the lead breaks (usually at the pliers) because you will find yourself flying backwards uncontrollably!

Although kinks can be removed from a lead came by stretching, nicks and most crush-damage can not. A problem with lead is that it is very soft and therefore very prone to damage especially on the leaves. At best you might be able to use a lead knife blade or an All Nova tool to “flatten out” some of the damaged areas but, of course, you will be cutting up the cames in various lengths so you can plan to cut pieces between the points of damage, or if you’re sneaky you can ensure damaged areas are soldered over at joints. Constructing a panel from damaged leads, visible for all to see, reflects badly on your commitment to excellence so don’t do it. Hiding little areas of damage under soldered joints is another matter entirely!

From all this you’ll understand why it’s not a good idea to buy coiled-up lead cames and why it’s sensible to transport and store them tidy and flat. I’ve previously suggested cardboard tubes, drainpipes and gutters as suitable storage containers.

If you don’t have space to store your cames in full-lengths then you might try cutting them in half but this will limit the maximum size of panel that you can make. Another reason to cut cames into half lengths is when you’re not a strong athletic person or you’re on your own – it’s easier to pull a shorter length of lead came single-handedly.

Use an All Nova Tool

The All Nova tool is inexpensive and replicates the functions of traditional tools such as the lathekin, fid, oyster tool and others besides for burnishing, flattening and spreading came. Unusually for “multi-function” tools, which tend to do many things badly, this one is well-designed and does all the tasks asked of it properly. I think it’s an essential tool for anyone who does copper-foiling or leaded light work. Not really useful for fused glass work though.

I’ve never seen any “formal” instructions on what the various parts of an AllNova tool are designed for so here’s my take on what I’ve read and discovered for myself and I also attach a picture that also includes a few horseshoe nails and a few scraps of lead came (the purpose for which will become apparent later).

DSCF3326 AllNova ToolThe outside curve of the flat face at the flat end of the AllNova tool can be used for burnishing copper foiled work or to completely close the lead came channel gap around the peripheral edge of a leaded light.

The very end of the flat end of the All Nova tool can pushed into the channel of a lead came and gentle “pulled along” the channel to open-out a kink in the leaves of a lead came, or the flat face can be used on the outside of the lead came to close-up a kink in the leaves of a lead came. Although this flat end of the tool is useful for dealing with kinks and opening-up the channels, see below for how the heel at the “pointy end” can also be used to widen the channel down a full-length of a lead came in one simple action.

Another use for the end of the flat side of the tool, when inserted into the heart of a lead came channel, is to help push and shape the lead came around the profile of an adjacent piece of glass. This avoids the kinds of damage that your hands or some other tool might do when pushing against the structurally weak leaves of the cames.

And yet another use for the flat end is to gently open up the “crushing damage” that can and often does occur when cutting a lead came. Insert the flat end into the channel just behind the damage and pull through to the end of the came. The little crushed area at the end will be pushed back into shape. I sometimes also use of the flat-side of a lead knife to “finish off” the damage repair.

An All Nova tool can be used to widen the channel of a lead came if glass is too thick to be inserted into the channel easily, or if the channel is slightly closed. The heel area at the “pointy end” is a splaying tool. Hold the came end that’s nearest to you and put the ‘heel’ of the AllNova tool into the lead came channel nearest to you. Then gently push down the heel into the channel and push away from you. The amount of pressure downwards into the channel will affect how much you splay the leaves of the came so take care. Ideally, practise first on a pieces of scrap came to get the technique right. You will see the channel widen by an amount determined by the downward pressure being applied. If the channel is still not wide enough for your glass then you can try to pull back with the ‘toe’ of the All Nova Tool (remembering to now hold the came at the far end!). To be honest, I’ve never needed to use the toe-end of the tool as the heel seems to do enough of a widening job for my purposes.

A traditional oyster tool (long thin U-shaped blade with a handle) is another possibility for widening the channel of a lead came. There’s not much point in owning one if you already have an AllNova tool.

If you’ve used the heel to widen a came and it’s now too wide then the flat end of the AllNova tool can be used to reverse the over-enthusiasm. Press the flat side down and slide gently along the came to close-up the gap. A sort of gentle burnishing action you might say.

The pointed end can be used as a “picking tool”, for which the most obvious task is to remove excess cement after waterproofing a leaded light. Despite this suggestion, I tend to use matchsticks because they can be then thrown away. The pointed end could also be used for back-scratching and nose-picking. Well, that’s what I tell kids. Some believe me.

And finally, what’s the little hole for? To be honest I have no idea.

Preparing for Construction

Place your paper cartoon design onto a wooden base and firmly fix a batten along of the main (longest) edge of the design so that the design cannot move and you have an accurate straight edge to work from. Of course, this assumes you have at least one straight edge in the cartoon design.

Ideally I would add another batten at 90 degrees (or whatever angle is required) to form the second edge of the panel to ensure at least two side can be constructed with absolute accuracy. This also gives you a firm and well-defined corner out of which you assemble the panel. Get the angle wrong and the resulting panel will also be wrong!

I tend to leave a little gap between these two battens so that a lead came can “poke out” of the corner if necessary.

Masking tape is not very reliable to hold a cartoon design firmly, nor will it ensure that two sides of the design are accurately placed, but it is better than nothing.

Cutting Lead Came

There are different kinds of commercially available lead knife that are commonly used. The traditional ‘Don Carlos’ lead knife seems to be more expensive and in my experience works no better than a more modern lead knife.

Modern lead knives have a curved blade on one end (with a pointed end on one side) and metal cap at the other end of the handle. The metal cap is intended to be used as a hammer and is useful for driving horseshoe/glazing nails into the base board. It is a boon for lazy people because it means you don’t have to repeatedly swap between a lead knife and a hammer. Take care not to cut or stab yourself with the lead knife blade when hammering the horseshoe/glazing nails – enthusiastic hammering is a bad idea with a blade not far from your face!

An inexpensive alternative to the “proper” lead knives are putty knife or a cut-down wallpaper scraper which has been sharpened on a grinding stone (of the kind you would sharpen a chisel for example). Be sure the blade is strong and does not flex.

Later I have included a picture containing an improvised and a modern lead knife.

Just as the secret of a good steak is a sharp knife, so it is true for cutting leads. A blunt lead knife is harder to use than a sharp blade so sharpen the blade regularly. I use my kitchen knife sharpener for this purpose and it seems to work well enough.

There is something of an art to the act of cutting a lead. To begin with, place your H-section lead with leaves top and bottom and the channels to the side. Then, with the lead knife correctly placed above, use a gentle side-to-side rocking motion whilst pressing downwards. The wiggly rocking motion helps to work through the considerable amount of lead in the top leaves of the came. When you’re about to get through the top leaves, reduce your downward pressure because relatively little is then needed to push down through the channel part. And finally, increase the downward pressure to push through the lower leave of the came. If you can keep your knife vertical (except for the initial “wobbling” action) throughout this process you will get a nice exact 90 degree vertical cut. A nice vertical cut ensures the lead work is equally precise on both sides.

Practise makes perfect but sometimes some trimming may be needed to get the piece of lead to fit exactly in the panel. Hold the lead came in the same way and pare away at the end of the came until the exact length and angle is achieved. If necessary, flip it over and repeat from the other side. Wipe away the little pieces of scrap because they can damage a came if you subsequently try to “work” on top of one of them.

Once cut and trimmed to size there may be some crushing damage to the ends of the leaves. In addition to using the flat end of an AllNova tool to “pull though” the end of the channel I also use the pointed end of the lead knife to deal with any residual damage to the corners of the came. Crushing damage becomes an unavoidable problem when cutting the cames at shallow joint angles.

Remember that it is easier to cut the stretched came into smaller pieces to work with than a full length but it will mean a little more waste. Shorter lengths of came are also less likely to get twisted or damaged when they accidentally knock into other things nearby.

Use of a mitred or butted joint corners are equally acceptable. The choice depends on circumstances and generally butted joints are quicker and easier. Remember that the joint will be soldered so how you form the joint will not be visible. All that remains visible is the quality of your soldering!


Glass cutting errors are not so critical for leaded lights when compared with copper foiling.  Actually we should be aiming for just a hint of “rattle” in an assembled leaded light because it tells you there are no “pressure points” that might cause stress fractures later.

Ideally you should strive for a situation in which you rarely need to use a glass grinder to finish off pieces of glass for leaded lights. Pause for a moment to think about the glass workers of times past when electric glass grinders were not available. Getting it right first time was important because all you had was grozing tool with which to “nibble” the glass and a scythe stone. So, let the “leaves” (flanges) of the lead came be your friend as they hide a multitude of sins, such as slightly mis-shaped pieces.

Assemble from the longest side of your piece first. It is usual to start the assembly in a corner that will at the base, working piece by piece away from the corner and up the side and across. Pieces of came will need to be cut enclose each successive piece of glass that is to be added.

Although it’s a rather vacuous statement, remember to pause from time to time as you assemble the piece to review progress and plan what needs to be done next. For example, sometimes you may find that you need to build a whole “sub-assembly” and add it as a whole rather than add pieces one part at a time. Remember that you are aiming to make the pieces fit accurately over the cartoon design as well as constructing a strong panel that will look good when soldered. This is not a trivial matter so that’s why I try to plan and record my cutting and jointing intentions directly onto the cartoon in the design stage.

To a significant degree your cartoon design ought to address many of the visual appeal and strength issues but there remains the matter of how you cut and connect those pieces of lead came. For example, running single continuous lengths along the outside of each edge of the whole piece is good for the strength of the panel. But what about a circle within the design – are you going to have a single piece of lead coiled all the way around? Where will you “make the join”? Try to think before cutting and fitting the leads. Better still, do it in the design stage!

To stop the assembly from slipping and falling apart you will find it useful to strategically hammer horseshoe/glazing nails around the edge of the part-constructed panel wherever they are needed to stabilise the panel. A dozen of these horseshoe nails is adequate for a modest sized panel.

Before you start hammering those nails into your baseboard and against the leads I remind you that horseshoe nails are made from harder metal than lead and can therefore damage the leads. I therefore recommend you place a piece of scrap came between the cames of your panel and the horseshoe nails as a softer protective spacer.

DSCF3281 LeadedAt this point I think I need to relieve your boredom with a picture. So, to illustrate what I have been talking about, look at the picture of the assembled panel. Notice how the circular area containing the rosebud has been pre-assembled before insertion. Notice also the little mistake on the right-hand leaf where I’ve inserted a little fillet of lead to “fill the gap”. I’ll talk more about this “bodging” when I chatter about soldering. Notice also the use of horseshoe nails with little scraps of lead to hold the assembly firmly in place. And finally, you might want to compare how I cut the leads with how I planned to do it against the cartooned design.

The outer perimeter of the panel does not need to be cut to exactly the right size to begin with but will need trimming when you have finished. This is why I mentioned that I often leave a little “gap” between the battens earlier on in my chatter.

But you may be wondering, especially as a novice, how to remove at least some of the guesswork from cutting the pieces of lead came accurately. Am I right?

Well, it depends on the situation as to how to proceed, but one extra useful hint is that a scrap of came can be used to “represent” what has not yet been fitted. It’s easier to show you than write it down but I’ll try…

Imagine you have a single piece of glass in your hand and that it’s a quarter of a circle. You want to cut the curved piece of lead but realise that the two straight sides of the quarter circle will also have leading. So, either the curved piece of lead needs to be slightly shorter than the length of the curved edge or the straight pieces need to be slightly shorter than the straight sides. Aaargh! This is partly why I think about the cutting plan at the design stage.

Let us assume the straight sides of the quarter circle will have full-length pieces of lead came and that the curve must fit in the remaining space. We therefore want the curved piece to be slightly shorter than the length of the curve of the glass piece. But how much shorter?

To remove guess work from cutting this curved came piece accurately,  first apply your piece of came to the curve and push it into shape along the curve. You could use the flat end of an AllNova tool to help you do this without damaging the lead came. Allow this length of came to overlap the ends of the curve at each end. We know we need to cut “something” off each end so need to figure out where exactly to cut the ends in order for them to both butt-up accurately onto cames running along the adjacent straight edges.

With the overlapping curved came still in place, lay short lengths of scrap came just next to the overlapping ends of the curves on each of the adjacent straight sides. These two scraps shows you where the real straight cames will fit. So, lightly mark the curved piece of came at each end with your lead knife with lines that extend the inside edges of the two scraps.

With the curved came marked, remove it, put it on a nice clean work surface, then cut through the came at the required angles at each end. The quarter circle of glass and the curved came are now ready to be added to the panel. If necessary hold them in place with a horseshoe nail and protective lead scrap.

DSCF3329 CuttingThe picture you now see is an illustration of what I’ve just been talking about and also includes of a lead knife made from a cheap wall scraper and a “proper” modern lead knife. If you click on the picture it will display in greater detail in another window.

Incidentally, I’ve deliberately used old lead cames for this picture so that you can see what happens after several years of storage in a relatively dry environment. Notice they are looking distinctly grey.

The upper-right area of the glass piece illustrates how a scrap piece of lead can be used (across the top) to gauge and mark where to cut the long curved piece of lead (on the right). The lower-left area of the glass piece shows the next step, where the lead has been cut and you should immediately notice that the curved lead does not reach the end of the curve. Notice also that when you follow the straight piece of lead on the left, downwards along the inner edge, it leads you neatly past the end of the curved piece. This illustrates what you’re trying to achieve with each pieces of lead came in the assembly.

But what happens when you later find that you have an assembled panel ready for soldering and discover that one of the leads was 1mm or maybe 2mm too short? Such accidents do happen but don’t despair. By all means investigate to understand how the problem happened, and learn from the mistake, but don’t dismantle the panel to re-make that piece of lead came because there’s a sneaky trick you can use and it’s another use for little pieces of scrap H-section came…

Although this trick may seem to relate to soldering, I’ve put it here because really it’s more about dealing with an assembly problem caused by mis-cut leads.

To fill in a rather-too-big gap easily and invisibly, first cut a suitable short length of the H-came that will nicely fit into the gap above and below. Then, use your lead knife to chop out one side of the H so that you end up with a T and an I piece (or two stubby T pieces if you prefer). These two pieces can now fill the gaps on each side of the panel.

When you are ready for soldering, insert the T-shaped portion to bridge the gap and solder as normal. The solder flows over the insertion and your trickery then is hidden behind the solder joint.

Later, when soldering the back of the panel, use the remaining I shaped piece but be careful you don’t lose it in the meantime. No, actually it doesn’t matter if you lose it as you can easily make another!

Defects larger than 2mm can also be dealt with in the same way, provided they are shorter than the size of the soldered joint to be produced. But, if you’ve got a gap larger than about 3mm you should start to wonder how you’ve managed to cut a piece of lead so badly wrong and not notice it before!

This trick is not needed for tiny sub-millimetre joint defects because solder will happily bridge small gaps.

If you refer back to the picture-before-last, you’ll remember I filled a little gap with a fillet of lead at the end of a rose bud leaf. On this occasion the fault was only on one side of the panel so I could simply bridge the gap on one side. Again, this becomes an invisible mend because it will soon be covered with solder.

Soldering Lead Came

If you are a novice with leaded light construction you will discover that soldering a leaded light is not the same as soldering copper-foiled work. For this reason I recommend you do lots of practise joints until you can confidently and reliably solder lead cames.

What I describe works for me but to be brutally honest I ought to practise my leaded light soldering more often because is “a bit dodgy” sometimes. Ask around and watch other people soldering and they will reveal subtly different techniques. With time you will find a technique that works reliably for you.

The key to successful soldering is preparation. With copper-foiled work your “safety flux” removes oxidised copper and this helps the solder flow and bond nicely. The situation with lead cames is subtly different because a different flux is used and oxidation must be removed before the flux and solder are applied.

Some people may tell you to use a fine-grade wire wool to remove lead oxides (ie “make it shiny”) in preparation for soldering. I have tried this method and although it works I have two objections to it. One is that it produces a lot of dust from the wire wool breaking down into fine iron particles. The second is that the rubbing process produces a lot of lead dust, some of which will become airborne whilst rubbing and also when cleaning-up afterwards. Lead is nasty when it gets into your body so, for your own health, don’t make lead dust when there is an equally effective alternative method that doesn’t!

The alternative to using wire wool is to lightly roughen the area around an intended solder joint with the point of a lead knife or a horseshoe or glazing nail or, in truth, anything else that’s sharp, pointy and can be used to scrape the surface of a lead came. You only need to get the surface shiny around the exact area where you will be soldering. This is simple, it’s effective and it’s not going to harm your health.

Now that you have some lead prepared and ready to solder, there’s an extra step I suggest, if you have the patience…

Take a moment to pack a small piece of cardboard or folded paper between the glass and lead came in the area where the joint is to be soldered. This preserves the gap, protects the glass and perhaps more importantly, it eliminates solder bead drops which may ultimately cause a stress fracture in the distant future.

Next is the application of the soldering flux. For leaded lights the flux is tallow and the form commonly used looks like a candle minus a wick. The tallow should be rubbed around the surface of the area to be soldered.

The method of soldering is also different from copper-foiled work. First feed a little solder onto your soldering iron so that it holds a molten bead.

If you’ve read my chatter about choosing the right solder then you know you ought to be using a 40:60 solder rather than a 60:40 solder and should understand why. But I digress…

The aim is now to transfer the solder bead from the soldering iron to the joint without melting the lead around the joint. Much practise is needed to achieve consistently good results and the most important thing to understand is that a confident and quick technique is the key to success.

Slowly bring down the soldering iron tip (with the solder bead), but try to stop when the iron’s tip is a millimetre or so above the lead came. At this point the solder will “find” the lead and begin to spread out by itself. Oh for the joy of surface tension!

You can then deftly move the soldering iron around (still trying to hover) to help the solder flow around to where you want it do go. The aim is not to touch the underlying lead with the soldering iron because you don’t want to directly transfer heat from the soldering iron into the leads and cause them to heat up and melt more quickly. I suppose this technique could be likened to rolling a blob of sticky glue around – the objective is rolling, not squashing.

The reason you need to act quickly and deftly is that the lead cames and the solder melt at similar temperatures and it does not take long for the heat in the solder to conduct into the lead, heating it up to melting point. This also explains why we don’t want the leads being heated up more quickly by being in direct contact with the soldering iron. So, speed and accuracy is important. Starting the process with cold lead is also important.

In my experience “fiddling around” trying to “fix” a bad joint rarely achieved more than melting the underlying lead and make a crisis out of a disaster. If you really must “fix” the joint, leave it alone and do not attempt to fix the problem until the joint has become stone-cold. I repeat this warning in different words to stress this point: do not be tempted to “fiddle around” when the lead is still hot because it’s nearly ready to melt!

Let us assume you’ve dropped your blob of solder, hovered with the soldering iron and have and wiggled and rolled the solder around to the point where it has satisfactorily covered the whole area of the joint. You must immediately  pull away the soldering iron because you don’t want the leads to melt.

And finally, an opportunity to clean-up as you go. As soon as the soldering iron has been removed, count a “slow 5” to give the solder enough time to become solid but not long enough to allow the tallow flux to solidify. It is now safe to wipe the soldered joint with a paper towel or a clean rag. This will remove excess tallow and save you a lot of difficult cleaning work later.

If you forget to wipe away after your “slow 5” then don’t worry. Bring your soldering iron reasonably close to the joint for just long enough to re-melt the tallow then remove the soldering iron and wipe away. Your objective is to gently melt the tallow and not to re-melt the solder!

Remember to remove your little piece of cardboard (or paper).

Waterproofing and Strengthening

In this section please notice that I do not use the word “putty” because it is the wrong word and the wrong product to be using when we concern ourselves with the waterproofing and strengthening our freshly soldered leaded panels.

Leaded light cement smells a little like ordinary glazing putty but looks different. Leaded light cement is usually dark coloured and always has a sloppier consistency. Both smell of linseed oil but leaded light cement smells more of turpentine (or substitutes). Another difference is that putty stays soft for many months, if not years, whereas the cement dries and sets within days. So, dear reader, there really is a difference between putty and leaded light cement.

If you’re not doing much leaded light work then remember that the leaded light cement will slowly “settle out” in the tin over the course of a year or two into a hard lump of solids underneath an oily top layer. Despite this, I have found that even after a few years of settling it can be “revived” and made usable again, but it is time-consuming process poking, mixing and squidging the solid and liquid portions back into something usable. This may be useful to remember if you’re short of funds but have plenty of spare time.

It is also a hint that you should not buy more than you need. Or, as an alternative, perhaps we should make our own, storing the dry and wet portions separately, then mixing only what’s needed when it’s needed. Oh dear. The formulation of leaded light cement. It’s another area I’ve yet to chatter about.

For the moment, I just warn you not to blindly follow the recipes that some people are publishing on the Internet. As you might expect, some are sensible but some of them are well-intentioned but reveal themselves to be ill-conceived on closer inspection. If some lengthy chatter about formulations for leaded light cement is important to you, please prompt me to do this sooner rather than later.

Right, back to topic of waterproofing and strengthening…

The general plan of attack in this stage of construction is to force the leaded light cement into gaps between the lead cames and the glass pieces. With the gaps filled we achieve a single solid structure. Over the course of a few days the leaded light cement hardens and therefore stabilises the panel and increases its strength. Once hardened the cement also forms a waterproof barrier.

The best warning I can give you is to not get too enthusiastic, trying to force too much into the gaps, because it’s only going to start oozing out of the other side of the panel. All you’re aiming to start with is to fill the gaps on the “upper” side of the panel. Once the whole process of waterproofing and strengthening is complete on one side, you can then flip the panel over and repeat on the “other” side. The elapsed time is days, not hours!

DSCF3286 WaterproofingHere is a picture to illustrate what I’m now talking about.

Waterproofing is a messy process so use plenty of newspaper under your work. Cheap throwaway toothbrushes and nail brushes are recommended for forcing the cement into the gaps. It is better to use throwaway items than buying and cleaning expensive brushes because the hardened cement renders the brushes useless. Can you see how messy the little nail brush is in the picture?

Another tip is that you can also use a piece of glass to ‘push’ the compound into gaps but I don’t tend to do this.

I should also mention that leaded light cement is fantastic at finding its way into the smallest cracks, crazes, and deep recesses of textured glass surfaces. Never forget that the cement can destroy the visual appeal of the most gorgeous piece of “unsmooth” glass with a patchwork of mucky marks that are impossible to remove. Protect the surface of any glass that has such surface imperfections by whatever means are available to you so that the leaded light cement can not find its way into these defects in the glass. An adhesive plastic film should work nicely, maybe even self-adhesive labels.

If you’re careful and don’t randomly slosh the cement everywhere then it’s going to be easier to “clean up” later. To this end, try to keep the cement close to the filled-gaps and do your best to not get the cement on the tops of the lead cames. Look at the picture to see how I try not to make too much of a mess but wasn’t entirely successful.

When you have cemented one side of the leaded panel it’s time to add whiting (see below).

Be aware that the volatile ‘drying agents’ in the cement are smelly so ventilation is suggested. It’s not that these vapours are toxic, it’s that their smell can be quite intense and last for days.

Once the whiting has been added, leave the panel overnight, clean-up that side of the panel then attend to the other side of the panel.


Whiting is nothing more exciting than chalk powder and it needs to be sprinkled over areas where leaded light cement has been applied. An alternative to whiting is to use fine sawdust or fine wood shavings. Whatever you use, just remember that the aim is to “draw out” the oily part of leaded light cement.

Plaster of Paris and patching plaster have also been suggested as an alternative to whiting but I’d be wary of them because any hint of dampness may cause them to solidify on the surface of your glass, making the cleanup process harder. Let me know if you’ve tried these alternatives as I haven’t.

DSCF3288 WhitingHere’s a picture of a panel that has just had whiting added. It still looks nice and white but in a few hours it will start to look rather mucky. Notice that I’ve tried to put more whiting where there’s more leaded light cement and less where there’s (hopefully) only glass. Notice also that there’s whiting on top of the leads because there’s cementing “mess” to be dealt with on top of the lead work.

So, don’t be mean-minded with the whiting. Use as much as is needed. As a minimum at least try to get most of the whiting where there’s cement. In addition to drawing out the oily part of the cement, whiting also helps to clump together particles of excess cement and as such is really helpful in the “cleaning up” activities.

After a few hours the whiting starts to clump and look mucky. Now you may clear excess whiting off the glass surface carefully with a soft brush or a cloth but stay away from the leaded areas as they have not hardened sufficiently. Try and leave decent border (at least 2mm) around the leaded areas completely untouched. Carefully removing cementing compound from the tops of the lead cames is another task that can be started. Adding more whiting or shuffling “unused” whiting to where it’s still needed can also be done. So, at this stage our aim is to remove the worst of the mess without compromising the quality of the waterproofing or strengthening.

On the next day, no sooner, remove the 2mm borders carefully with a wooden stick, matchsticks, an All Nova tool or similar. This is where I mostly use used matchsticks. If you used enough whiting then the cement will have set sufficiently and this becomes quite an easy job. The clean-up process is all done when all the gaps between glass and lead are filled with cement and there are no stray lumps of cement on the lead cames or on the glass. Try not to under-cut the cames when cleaning away the excess cement because all it achieves is little water collection areas which are ideal micro-habitats that encourage algal growth especially in damper climates.

Once cleaned up, it will still take a few days for the remaining “drying agents” to evaporate out of the cement. As time passes the stink slowly subsides.


Some people suggest that soldered joints should be darkened to match the lead work. Zebrite is a commercial product that can be used to blacken the lead and solder and is normally used to blacken stoves. Zebo is an equivalent product that is no longer made.

My experience is that these products don’t really work very well, except on stoves. They hardly take to solder and aren’t much better with fresh lead. So an alternative suggestion is to patinate (ie use patina) these areas first.

Better still, in my view, is to not bother with this step. Allow the lead and solder to do their darkening naturally.


Here are a few miscellaneous things that I couldn’t sensibly put anywhere else:

An alternative to using a grinding stone or grinder to remove a burr from glass is to run a piece of scrap glass down the edge of the cut edge. Quick and good enough for leaded light work. Another handy trick from the days before electric grinders.

Smooth side outside and textured inside is the old general rule for glazing leaded lights. This is simply because single-glazed windows get dirtier outside than inside. However, this becomes questionable when the panel is part of a double-glazed window pane or embedded into a triple-glazed window pane. For indoor decorative pieces it’s a matter of design because you might deliberately want people to touch and experience the different surface textures.


I do not tend to get involved with the installation of leaded lights so only have a couple of thoughts to pass on.

Using glazing putty to mount a leaded light panel into a window frame has been a standard practise for many years. It works and there are no nasty side-effects. Our ancestors knew what they were doing.

By contrast modern squirty plastic “caulk” type fixatives should be treated with caution as I have learned from personal experience. By “caulk” I am thinking of the kinds of product that you would use to seal the gaps around door frames or around a bath or sink. Take care with these products and check the labelling to see what happens when they “cure”. If the product produces a vinegar smell as it “cures” a consequence is that it will be prone to provoke a white powdery surface patina of lead acetate on nearby cames. Lead acetate is a far greater risk to your health than the lead of the cames.

Sometimes a leaded light panel is added as an indoor secondary panel against an existing window. I have seen double-sided sticky black butyl tape being used to attach the perimeter of a leaded panel to the perimeter of the pre-existing glazing. A typical location might be the window pane adjacent to a door.

Health & Safety

Last but not least is the dreaded Health and Safety section. It’s a must because we’re working with lead.

Working with lead cames to produce leaded lights raises a number of heath and safety issues and some of them I’ve already alluded to. I will now elaborate.

A guiding principle in health and safety is that the elimination of a hazard is always preferred to doing something that reduces the effects of a hazard which in turn is preferred to the use of protective equipment to “hide” from the hazard.

Lead cames and particles of lead are not, in themselves, toxic. It is the compounds of lead that are what we should be most worried about. It is biological and chemical actions that turn lead into compounds of lead that you need to be most wary of.

Already mentioned is lead acetate from “caulk” that may arise when mounting and installing a panel. Lead acetate is a compound of lead. It is a white powderly “bloom” and easily inhaled or injested if you don’t take care.

Another source of lead compounds is through the action of sweat on our fingers reacting with lead when we handle lead came or solder. So, although touching lead is not very much of a hazard to your health, the ingestion of lead compounds produced by the sweat on our fingers is bad news. The transfer route that leads to ingestion tends to be lead came to fingers to mouth. So, before you try eating, drinking and smoking, stop working with the lead and wash your hands first.

Ingestion of particulate lead and lead compounds can be caused by airborne particles and I’ve already explained why I do not use wire wool on lead cames. So, rather than waste time and money using cheap ineffective face masks, eliminate the creation of particular lead by not using wire wood to clean up lead cames.

Although not directly lead-related, remember horseshoe nails and modern lead cutters that double-up as a hammer. Here you need to be careful not to cause puncture wounds and cuts. Puncture wounds and cuts must be covered with sticking plasters when working with lead or other toxic chemicals. Cuts and wounds are a fast and efficient entry point into your body.

If you’re a bit paranoid, you might consider using some rubber or nitrile gloves to minimise your contact with lead. But don’t let these gloves lull yourself into a false sense of security – remember to wash your hands after you take them off.

Lead poisoning is one of the oldest occupational hazards due to lead mining over many centuries so a word about exposure limits is perhaps needed. The first point to make is that different nations have different legislation so I can only generalise.

Lead exposure limits are unlikely to be exceeded if you’re an occasional hobbyist. The trouble is that workers only occasional exposed to lead, and hobbyists, are not really in a position to measure lead exposure without outside help. If you are in the least worried, try talking to your medical doctor, or your employer’s occupational health service (if you have one).

The group at risk is full-time workers who spend a lot of their time working with lead and traditional lead-based solders.  If you are an employee in a company where working with lead is a significant part of your job then your employer ought to be monitoring your lead exposure routinely through periodic medical assessments. I say “ought” rather than “will” or “should” because theory and reality are rarely the same.

The world is full of experts in Health and Safety and unfortunately a lot of health and safety is about subjective opinion rather than reasoned facts. Unfortunately this leads to experts that are, to varying degrees, ill-informed, paranoid, obsessive, irrational, deliberately biased or downright dim-witted. Somewhere amongst the cacophony of mixed messages is a reasonable and rational basis on which to live our lives!

If you think I should do a blog on Health and Safety that identifies some of the hazards and risks of our activities and translates them into advice that is hopefully more balanced, rational and helpfully practical then please tell me that it’s something you want sooner rather than later.

A Topical Postscript

And finally, on the subject of Health and Safety, you may already be aware of what’s happing in Oregon in the USA.

I note with concern that “the authorities” in Oregon are behaving irrationally and badly towards glass producers Bullseye and Uroboros. You will find more information in the news releases section at the Bullseye web site. It makes interesting reading because it relates to to toxic metal emissions from furnaces.

The recent announcement by Spectrum that they are shutting down makes this even more worrisome for our chosen career or hobby.

This health and safety madness in Oregon reminds me of a quote attributed to Voltaire:

It is dangerous to be right when those in power are wrong.

Or perhaps this one from the painter John Constable:

We see nothing until we understand it.

Bye for now, dear reader. Thank you for visiting my blog.




Posted in Cartoon design, Flux, Glass Cutter, Lead cutter, leaded light, Leaded light cement, Putty, Solder, Soldering, tallow, Whiting | Tagged , , , , , , , , , , , , , , , | 4 Comments