When working with glass it is important that all the glass used has the same coefficient of expansion (COE). In this project I'm using Bullseye glass and dichroic glass, both of which are COE90.
Always wear safety glasses when working with glass and take care not to cut yourself. Small cuts, however, are unavoidable so keep some plasters handy.
To make this cabochon we are, in effect, making a glass sandwich with the dichroic glass as the filling. If you use a solid piece of dichroic glass as a base you have only to top with a layer of clear glass.
Score the glass with steady even pressure then line up the mark on the top of the breakingpliers with the score line. Squeeze gently. Thin glass can be broken by holding firmly at ech side of the score line and rolling the wrists outwards.
To cut the clear glass slightly larger than the base, lay the base on top of the clear glass. As the cutting wheel is away from the edge of the cutter, the clear gklass will be a little bit bigger. Cut some pieces of dichroic glass to go in the sandwich. Clean the glass with methylated spirits. You can use clear nail varnish to stick down small pieces. The piece is now ready for firing.
The firing temperature depends on the effect you want to achieve and also on your kiln so you will need to experiment. You can always fire again if necessary.
For well-rounded cabochons, fire to 795 degrees Celsius and soak for 30 minutes; then cool to 550 degrees Celsius and hold the temperature for 30 minutes to anneal the glass. Annealing takes the stress out of the glass.
For more defined freeform shapes, fire cooler to about 780 degrees Celsius and don't soak at the top temperature.
Please Note: These temperatures are for Bullseye COE90 glass. Different COE glass has different annealing and firing temperatures.
If after firing some of the cabs are not as you would like them to be, you can:
Tutorial written by Jill Egan
You will find more of Jill's work on her website Kiln Fired Art