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GBCG - Generic Base Crystalline Glaze

Modified: 2022-10-13 21:46:36

Cone 6-10 - Almost all other Frit 3110 recipes are based on additions to this

Notes

From Crystal Glazes Book 1 by Fara Shimbo, page 37.

Almost all other recipes are based on additions to this.

The more frit you use (relative to the other ingredients), the lower will be the maturing point. That being said, almost all of the recipes here have close to 50% of this frit. The more silica, the less the glaze will tend to craze, but the fewer the crystals produced. Zinc silicate is Zn₂SiO₄, so for every molecule of ZnO, two SiO₂s are needed to form the crystals. Of course the crystals are on the surface and make up only a small part of the total glaze volume, that leaves extra SiO₂ for the glaze itself. In this recipe the SiO₂:ZnO ratio is 2.5:1. Understandably, raising and lowering the amount of zinc oxide will directly affect how many crystals the glaze will be able to grow. That being said, almost all recipes here have 25% zinc.

The recipes here add small amounts, usually 5-10%, of other materials, usually at the expense of the silica. The most common addition is titanium dioxide. MgO is added using dolomite, talc or magnesium carbonate. Li₂O is sourced from spodumene and lithium carbonate. CaO from whiting or dolomite. Tin oxide is also used. These additives affect opacity; crystal size, shape and ancillary development; and color. In a couple of instances, other frits are also used. There is much more background information in Crystal Glazes books 1 and 2 (specifically about this in book 1 page 37).

Related Information

Crystal Glazes book 1

About understanding the process and materials. Mixing, applying and firing crystalline glazes is very different than with stoneware or porcelain. By far the best success is had by people willing to learn about materials and chemistry and experiment with recipes and firing schedules. A lot of things can go wrong and hundreds of firings are needed to develop a style and repertoire of glazes. There is even a "language of crystals" to learn, being able to describe things using the right terms is a big part of development and getting and giving help to the community.

Crystal Glazes book 2

This is more technically oriented than the first edition, a book for those who are really serious about "learning the glaze", rather than just "doing it". It has fewer glaze recipes, highlighting and explaining the really good ones and their special qualities of crystal shape, amount of crazing or maturing temperature. This book has more about firing, both gas and electric. And more about clay bodies and better information about the glaze materials, coloring the background and crystals, seeding the crystals and the firing schedules.

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