IMPORTANT: The most important thing when working with glass is to make sure the glass is compatible with the project you are working on. Glass is rated off of a Coefficient of Expansion (C.O.E.) rating. This rating is given to glass based on how it expands and contracts. Therefore, you cannot fuse glasses with differing C.O.E. rates together or it will break!
Annealing & Soaking
Annealing is the process of slowly cooling glass after it has been formed. Annealing glass is typically done at roughly 950-960F°. Annealing helps the glass not to crack. It makes the molecules in the glass vibrate to get the stress out of them. This is done in bead making as well. It allows the beads to become strong and not brittle. This process takes about an hour to fully soak the glass.
Soaking is a term used frequently in these processes and it means to hold the product at a certain temperature for a certain period of time.
Glass fusing is simply the process of stacking two or more layers of compatible glass together to make a design, and then placing the stacked glass into a kiln, where it melts (fuses) together.
Tack Fuse: This process is done at the lowest temperature of 1350-1370F which will allow the glass to stick together but keeps its edges and form until it starts to exceed this temperature.
Medium/Soft Fuse: This is done at 1400-1450F and will cause all the glass to have softened rounded edges.
Full Fuse: This is the process where the glass becomes fully fused together. This allows the surface to be fully smooth without any texture. This process is done at 1450-1470F.
Slumping & Casting
Slumping : The forming stage of warm glass work that allows you to shape your fused projects into beautiful and functional items by heating them just enough to bend or ‘slump’ them into ceramic/or metal forms. This process is normally used to make plates, bowls, platters and other decorative art. Slumping range of most glass 1200°F to 1300°F.
Casting: A glass firing technique using hollow or open faced molds to contain and shape the melting glass. Glass Pasting or also known as Pâte de Verre is done at 1300°F to 1400°F. This casting technique uses finely crushed glass and produces a textured or frosted surface look. Cavity or Open Face is done at 1450°F to 1700°F. These firing temperatures for casting range significantly based on sizes and thickness of both the molds and the glass that is being used.
Temperatures used to make glass art:
- 1200°F Draping – glass softens enough to bend over a mold.
- 1250°F Slumping – glass softens enough to bend into a mold.
- 1300°F Fire Polish – glass melts enough to produce a surface polish.
- 1350°F Tack Fuse – pieces of glass will permanently fuse together.
- 1450°F Full Fuse – pieces of glass will fuse and melt to a single level.