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.
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.
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.
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!
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.