Before Starting

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.

Tools Needed

  • Oil filled glass cutter
  • Breaking pliers
  • Metal ruler
  • 2 pairs small pliers

Cutting Glass

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.

After Firing

If after firing some of the cabs are not as you would like them to be, you can:

  • Fire again to round off more
  • Top with another layer of clear glass and fire again, this is especially useful for textured glass
  • Grind into shape using a glass grinder, you might want to re-fire but usually the bezel strip covers the edge anyway.

Further Suggestions

  • Textured glass is more difficult to cut, turn the glass over and score on the smooth side, then using the metal ball on the end of the cutter, tap underneath the score line until the glass breaks.
  • The clear layer of glass often has to fill in gaps, so cut the clear glass marginally bigger than the bottom layer.
  • Soaking in the kiln (holding the top temperature) will round off the glass more.  If you want defined shapes, fire to a cooler temperature and don't soak.
  • If you cut the corners off the glass, the piece will be more rounded when fired.
  • To make small round cabochons, cut a 1cm strip of dichroic glass and a strip of clear glass.  Cut into 1cm squares; these will become perfect rounds when fired.
  • If the fired cabochons are not the shape required, or if they are too big for your bezel, grind them using a glass grinder.
  • Decal sheets for ceramics can be cut with a craft punch or scissors and fired over a cabochon to give an etched dichroic look or to cover unwanted bubbles.
  • Overglaze enamels and precious metal lustres can also be used over glass cabochons.
  • If the cabochon doesn't turn out the way you had envisaged and all else fails, hit it with a hammer and refire or use as frit.
  • If you grind the edge and wish to refire, first scrub the edge of the cab with a toothbrush under running water otherwise the edge will be cloudy when fired.


Tutorial written by Jill Egan

You will find more of Jill's work on her website Kiln Fired Art


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