Ready for a science lesson?
When I posted this photo of my leftovers at the end of a torch session, many people asked, “Why not just melt those bits down?”
I don’t melt these down because this day I was using two different types of glass, Effetre and Bullseye and they have different COEs.
COE - Coefficient of Expansion. It’s how much a glass will expand with heat. Or how much it will contract when it cools down. What this means to a flameworker, each COE will expand and contract at different rates. If you put two different glasses (say Bullseye and Effetre) together in the same bead, they will cool down at different rates and crack. The bead blows up. This is why beadmakers pick a COE and only use that one. Having two different glasses on your table is a recipe for disaster. Trust me on this one.
So why am I using 2 different COEs? Because that beautiful lime green is only available in Bullseye and I must have it. It as an intensity that brings life and spark to my jewelry. Like most beadmakers I use Effetre (made in Italy) almost exclusively. I like it because of the range of colours and also because with a COE of 104 it is very soft. “Soft” means it melts quickly and is very pliable so it is easy to manipulate. Bullseye, an American glass, has a COE of 90 and I find the colour palette a bit more muted and I don’t do muted.
The other type of glass used by some flameworkers is borosilicate or “boro”. This has a COE of 33 and is stiff. Not my style. Boro requires a bigger, hotter torch and is used more for sculptural work. If you’ve ever seen flameworkers using clear glass to make small animal sculptures, that’s boro.
So now you know about COE.
Sailorgirl Jewelry - happy, pretty jewelry AND educational!