How does glass “fuse” together?
The glass I use starts out as sheets of hard, breakable stuff. So how do I make this very hard material change shape, become malleable, and permanently stick to other layers of glass? The trick is to heat the glass in a kiln to such high temperatures that the glass actually melts. But there’s more to it (it’s never that simple is it?)…
Some glass cannot ever fuse together. Here’s why: when the glass melts, it expands; when it cools, it contracts. This rate of expansion/contraction is actually what determines whether one sheet of glass will bond to another sheet of glass. It’s called the Coefficient of Expansion or COE.
Not all sheets of glass have the same COE, and you can’t bond two sheets of glass together unless they have the same COE. If you try to bond glass of different COE, the project will crack when it cools because the sheets of glass will each contract at their own special rates…which won’t be the same. So the first clue to making sure that layers of glass will fuse in the kiln after they’ve melted is to use the same COE for all glass in your project. I use glass with a COE of 90.
By the way, this is also why I can’t use scraps of recycled glass for my projects…even though I’d love to do it…because they’re not COE 90 and won’t fuse to the dichroic and other fusible glass that I use.
When glass is heated, it softens and if more heat is applied, it begins to melt and flow. When two or more pieces of glass are heated together at first they will stick, or tack together. When heated further, they will melt together, flatten out, and become one solid piece of glass.
Once layers of glass are fused together, they do not spontaneously unfuse. If layers of glass separate after having been fused together, it is because the piece was traumatized by some kind of force (like dropping on the floor) and the point of breakage will be the weakest area near the impact.
I once had a customer find me at a show and tell me her FOXY Rectangle pendant spontaneously split into the 3 layers. Since I know glass does not unfuse once fused, I knew right away the piece had been dropped or banged against something. Still, an unhappy customer is not very FOXY, so I offered her a very significant discount towards a new piece. My customers must be FOXY at all times!
If you have a FOXY Rectangle that has split cleanly upon impact into the respective layers, it is possible that I can refire and repair the piece. Send me a photo and I’ll give you my expert opinion. Worst case, you’ll get a hefty discount on a new piece!
If you have a FOXY Circle that has fallen and broken or been chipped, I may be able to refire it as well and fix it. These actually are a little easier to repair…so send a photo if you need this service.
