Glass fusing is the technique used to join glass pieces together by partly melting the glass using high temperatures. The heating is commonly undertaken in an electric kiln. Instead of fitting glass together using a lead solder, 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.

Fusing is becoming a more and more popular technique, and it allows for a very exact planning of different colors within a piece. This method can be used for intricate stained glass windows. It also can be used with paints. Miriam diFiori from Italy is a master of this technique. Often, the initial product - a flat slab of glass - is fired a second, third, or even fourth time to form a three dimensional shape.

Glass, when made hot, can be formed in a process called slumping. This is done by heating a pane of glass to the point at which gravity pulls the glass into the form of the mold that the pane has been placed. This process can be used to make plates and bowls, among other things.