You can make fused glass in any kind of kiln. Fused glass fires at 815 degrees C, and a pottery kiln easily reaches this temperature. The kiln requires no modifications for fusing glass, but adding a few extra layers of kiln wash keeps any of the glass from sticking to the shelves or the bottom of the kiln. Once the glass is fired (cooked) in the kiln, it comes off of the coated shelves easily with very little residue left on the finished glass piece. Access to a kiln and basic knowledge of using a kiln is required for making fused glass.
Paint a thick layer of kiln wash over the bottom of the kiln and over the kiln shelf. After it dries, paint two more layers. Do not fire the kiln until the next day.
Clean out the kiln with the vacuum. Ceramic dust embeds in glass if it isn't cleaned out. If the dust cooks into the glass, you can't remove it.
Put a piece of glass on a flat surface, and add layers of different coloured glass on top of the first piece. Lay a clear piece of glass over the top.
Lay the kiln shelf into the bottom of the kiln. Place the stack of glass onto the kiln shelf. Turn the kiln on low for one hour. You need to warm the glass before turning the kiln to a high temperature.
Change the heat in the kiln to high, and let it heat for three hours. This gives plenty of time for melting the glass. As the glass cooks, air bubbles move through the glass making patterns and designs.
Turn off the kiln. Let the kiln sit overnight with the lid closed. Do not open the kiln until the next morning. The heat in the kiln anneals (strengthens) the glass.
Remove the kiln shelf from the kiln using pot holders. The kiln might be too warm still. Lift the glass off of the kiln shelf, and rinse off any kiln wash that sticks to it with water and a stiff scrub brush once the glass is totally cooled off.
If you use a clear piece of glass on the bottom, and put a layer of broken coloured glass on top, the colours blend together creating beautiful patterns.
Some artists maintain the temperature at 593 degrees C or 635 degrees C for 30 minutes. This step isn't required, and the glass fuses correctly without the step.