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.



About chatterglass

Maker of stained glass frippery.
This entry was posted in Dichroic Glass, Microwave kiln and tagged , , . Bookmark the permalink.

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