The Fused Glass Process

My interest in glass began in 1994 after visiting the Bullseye Glass booth at NCECA. At the time, Bullseye was encouraging potters to add glass frit to their pottery as an additional design element.

With the arrival of computer controlled kilns, fusing glass became much easier to manage. The computer can be programmed with a specific firing schedule that includes the critical annealing phase. To date I have had success painting with frit and kiln casting glass.

Frit is made in a number of colors and sizes; from powder to large chunks of glass. The powder, which resembles granulated sugar, can be used to make an overall design. When the design is complete the glass piece is fused in the kiln. In the fusing process the frit design becomes one with the base glass.

When making a large bowl, I start with 2 – 3mm, 12” round pieces of Bullseye cut glass rounds. One piece is cleaned and placed on the kiln shelf. The second piece is cleaned, and then a design added with frit. The second design piece is placed on top the glass already in the kiln. The 2 glass pieces and frit are fused together into a 6mm disk. In a second firing, the disk is slumped into a mold to make a bowl shape.

Kilncast Glass: Box Casting / Casting Glass Objects

Kilncasting glass is extremely technical and the steps to the finished product are tedious. I have been successful at open box casting and glass kiln casting techniques using a crucible. The open box castings required over 84 hours in the kiln to slowly cool the glass during the annealing phase.

Kilncasting requires a model be made from waxy oil clay. Once the model is made a casting is made, the model is removed and the negative space is filled with investment material. Once the investment model is made, it can be removed from the mold and placed in the box casting. More investment is poured around the model, dried, then cleaned and placed in the kiln.

Billets of glass are measured, broken and stacked on top of the investment model inside the box mold. Depending on the thickness of the mold it can take several days to fire and cool. Once the glass is cool it can be removed from the box and the investment cleaned from the glass. What’s left is a heavy piece of square, cast glass that can be up to 4 inches thick and will stand on edge. It’s dramatic, unusual and beautiful.

Casting a 3-D object uses a slightly different technique. Again, a model must be fashioned from oil clay. A casting must be made of the model. Wax is poured into the negative space in the casting. Once the wax casting is cool, investment is poured around the wax model. An area at the top is left open. Once the investment block is dry, which can take several days, the wax is melted out of the mold. The block is placed in the kiln. A crucible with billets is placed over the mold. When the glass becomes hot it flows (like corn syrup) from the crucible into the mold. This process takes days in the kiln to complete at a variety of temperatures. Once the glass is cool, the glass casting can be removed from the mold. This process is lengthy from the standpoint that it takes time to create the model, remove the wax from the investment mold, dry the investment, fire and cool the glass. Therefore, I believe the object that’s being created must really be worth the time and effort!