Monthly Tech-Tip | No tracking! No ads! |
Glaze fit. The left-most clay mug contains no talc (Plainsman Buffstone), the centre one about 25% talc (L212) and the right one is about 45% talc (L213). Talc raises thermal expansion. The centre glaze is G2931K, it is middle-of-the-road thermal expansion (Insight-live reports it as 7.4) and fits the low-talc bodies (and Zero3 porcelain and stoneware). But it crazes on Buffstone and shivers on L213. The lesson is: Forget about expecting one clear or base glaze to fit all low fire bodies. But there is a solution. I adjusted it to reduce its expansion to work on zero-talc porous bodies and raise it to work on high talc bodies. How? By decreasing and increasing the KNaO (in relation to other fluxes). The three fire crystal clear and work the best in a drop-and-hold firing.
Recipes |
G2931K - Low Fire Fritted Zero3 Transparent Glaze
A cone 03-02 clear medium-expansio glaze developed from Worthington Clear. |
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Recipes |
G2931L - Low Expansion Low-Fire Clear
A cone 03-02 low expansion clear ceramic glaze developed from Worthington Clear. |
Recipes |
G2931H - Ulexite High Expansion Zero3 Clear Glaze
A cone 03-02 higher expansion fritted clear glaze developed from Worthington Clear. |
Glossary |
Glaze fit
In ceramics, glaze fit refers to the thermal expansion compatibility between glaze and clay body. When the fit is not good the glaze forms a crack pattern or flakes off on contours. |
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. |
Articles |
The Majolica Earthenware Process
How to make strong, durable functional ware from red terra cotta odies based on the traditional of majolica. |
Firing Schedules |
Low Temperature Drop-and-Hold
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