Crackle glazes are most often understood as simply recipes that somehow form a crack pattern. But there is an advantage to seeing them in terms of the mechanism their oxide chemistry produced. Crackle glazes almost always have very high levels of Na2O and/or K2O (collectively referred to as KNaO). These two have the highest co-efficients of thermal expansion, by far, of those commonly found in pottery glazes. Feldspar is the key source. Not surprisingly, high feldspar (or nepheline syenite) glazes most often crackle.
Shown here is the 77E10A recipe, originally from Luke Lindoe. It is simply Nepheline Syenite and water (shown on three types of clay bodies). 77E10A1 and 77E10A2 are improvements on this, both provide a path to develop and adapt it for your needs.
| Glossary |
Mechanism
Identifying the mechanism of a ceramic glaze recipe is the key to moving adjusting it, fixing it, reverse engineering it, even avoiding it! |
| Glossary |
Crackle glaze
Crackle glazes have a crack pattern that is a product of thermal expansion mismatch between body and glaze. They are not suitable on functional ware. |
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