Q&A: Soluble Salt Migration



Jeff Zamek Ceramics Art + Perception 108 2018 Technical Home

Most potters have experienced the effects of soluble salt migration in a clay body that can occur in the drying, bisque, or glaze firing stages. The industry term is ‘scumming’, and it presents itself as efflorescence, or white crystal powder, forming on the surface of the clay.

The industry term is ‘scumming’, and it presents itself as efflorescence, or white crystal powder, forming on the surface of the clay. It can be observed on random parts of the clay body surface but is most often seen on edges or high points which dry faster than other parts. Faster drying increases the ‘wicking’ action of the soluble salts that travel to the surface of the clay with the evaporating water. Textured surfaces or the ridges on cup handles can reveal a hard-discolored crust on the fired ware.
In the bone dry or bisque state, fingerprints

Why does my clay have a white irregular crystal surface when it is drying?


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