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On the left is G2931J, a zinc alkali fluxed and high Si:Al ratio glaze. Those look like micro-bubbles but they are much more likely to be micro-crystals (high-zinc and high-silica is the mechanism for crystalline glazes). G2931K on the right has much more boron, double the Al2O3, less SiO2 and is magnesia-alkali instead of zinc-alkali. It is the product of dozens of tests to find an ultra-clear having a glassy smooth surface. This particular chemistry, although having only a 6:1 SiO2:Al2O3 ratio is ultra-gloss. In addition, it has low expansion, will fast fire and the boron is not high enough to compromise the hardness.
| Recipes |
G2931K - Low Fire Fritted Zero3 Transparent Glaze
A cone 03-02 clear medium-expansio glaze developed from Worthington Clear. |
| Oxides | ZnO - Zinc Oxide |
| Glossary |
Formula Ratios
The ratios of individual or group oxide molecule numbers are indicators of things like fired gloss, durability, melting temperature, balance, tendency to craze, etc. |
| Glossary | Glossy Glaze |
| Glossary |
Low Temperature Glaze
In ceramics, glazes are loosely classified as low, medium and high temperature. Low temperature is in the cone 06-2 range (about 1800F-2000F). |
| Glossary |
Transparent Glazes
Every glossy ceramic glaze is actually a base transparent with added opacifiers and colorants. So understand how to make a good transparent, then build other glazes on it. |
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