Written records show the glass casting process dates to the second millennium B.C, possibly in Mesopotamia, to produce jewelry and glass sculptures. Today, artists cast glass by creating molds consisting of silica plaster. A rubber form is made from the original sculpted clay model. From the rubber form, a wax model is made. In a process called investment, a cast of the wax model is made using a high temperature refractory plaster.
The refractory mold is then hand filled with layers of powdered or chipped glass. The heat resistant mold is placed in a kiln with a funnel-like refractory opening which is filled with additional solid glass granules or blocks. The kiln is heated to a high temperature, normally around 1450 degrees Fahrenheit. The glass melts, filling the mold. The glass is then cooled very slowly to room temperature. The mold is broken open, revealing the piece. Several days are spent refining the piece using grinding and polishing materials. From start to finish, pieces may take weeks or months to complete.