Friday, August 17, 2012

What is Fused Glass?

Most people are familiar with stained glass - that doesn't use heat and is called "cold glass". Glass blowers and lampworkers (beadmakers) use a torch, so that is called "hot glass". When a special type of glass is heated in a kiln, we call that "warm glass" or "kiln-formed glass".  (One of my kilns is pictured above)

Fused glass is a form of kiln-formed glass.  The temperature at which it is melted determines the result: at around 1350 degrees farenheit, it is called "tack fuse" where the pieces bond but don't entirely melt. When you ramp up to about 1500 degrees, you have a "full fuse" where the pieces literally melt together, creating a totally new shape and combination of glass.

There are other types of warm-glass techniques.  "Fire polishing"is done at around 1200 degrees to re-finish the edges of a piece that has been shaped on the grinder. Another method is  "slumping" where you fire a solid piece of glass in a mold, such as in making a plate, and "draping" where you lay it over a form, such as for a lamp shade. And kiln casting or glass casting is where you put bits of glass called "frit" in a mold and heat until it melts to the shape of the mold.

The glass used in fusing is a special type, and it has what is called a COE - coefficent of expansion. The common ones used for fusing are COE90 or COE96. The important thing about that is you CANNOT mix the two types together - they will not bond to each other. The major suppliers of fusible glass are Bullseye for COE90 and Spectrum for COE96. There are other COE's (like 104) used primarily by lampworkers (bead making) and glass blowers.

Fusible glass may be opaque, transparent, iridescent, textured, and dichroic. I will talk about dichroic next time.

Hope that helps you understand a little bit about what I do!


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