Glass fusing is the technique used to join glass

Glass

Glass is an amorphous solid material. Glasses are typically brittle and optically transparent.The most familiar type of glass, used for centuries in windows and drinking vessels, is soda-lime glass, composed of about 75% silica plus Na2O, CaO, and several minor additives...

 pieces together by partly melting the glass using high temperatures. The heating is commonly undertaken in an electric kiln

Kiln

A kiln is a thermally insulated chamber, or oven, in which a controlled temperature regime is produced. Uses include the hardening, burning or drying of materials...

. Instead of fitting glass together using a lead solder

Solder

Solder is a fusible metal alloy used to join together metal workpieces and having a melting point below that of the workpiece.Soft solder is what is most often thought of when solder or soldering are mentioned and it typically has a melting range of . It is commonly used in electronics and...

, two or more pieces of glass are laid on top of or overlapped on each other and are fired at temperatures ranging from 1100 to 1600 degrees Fahrenheit (750 to 850 degrees Celsius). It is important to realize that glasses with different coefficients of expansion cannot be fused together - upon cooling or after a certain period of time, the fused piece will crack. Many people who work in glass fusing restrict themselves to one brand of glass (e.g. Bullseye, Uroborus, Baoli) which is guaranteed to be compatible with any other glass from the range of fusible glass offered by that particular maker.