This is M340, it is not made from a mixture of 200 mesh refined minerals and ball clays, rather, from minimally processed natural mined clay. It is ground at 42 mesh, so the material contains a wide range of particle sizes. Potters who have only used this type of body are at home with it. Its advantages include excellent dry strength, pleasant texture, natural fired character, easy glaze fit and low cost. But downsides are lower plasticity, higher drying shrinkage and splitting. But a case this bad is not normal, it only happens when there is a "perfect storm" of factors:
The best way to prevent this from ever happening is to do the opposite of all the factors just mentioned.
| Troubles |
Splitting at the Plastic Stage
Pottery clays can split or tear at the plastic stage, sometimes ware can fall down right in front of your eyes. Understanding why is the key to avoiding the issue. |
| Glossary |
Clay Stiffness
In ceramics, clays exhibit plasticity in accordance with their recipe but also the water content. Each types of forming method has an ideal combination of stiffness and plasticity. |
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