The incredible plasticity of bentonite. It is the secret to win the ThrowDown!

Wednesday 17th April 2019

The 20cm vase on the left is insight-live.com/glossary/359">thrown from what I thought was a very plastic body, M370. I achieved close to the same thickness top-to-bottom (5mm). The one on the right was the same original height, 20cm. But it has dried down to only 18cm high, it shrinks 14% (vs. 6% for the other). The thinnest part of the wall is near the bottom, only 2mm thick! How is it possible to throw that thin? The body is 50% ball clay and 50% bentonite. Bentonite, by itself, cannot be mixed with water, but dry-blended with fine-particled ball clay it can. That bentonite is what produces this magic plasticity. But it comes at a cost. It took about four days to dewater the slurry on our plaster table. And one month under cloth and plastic to dry it without cracks.

Pages that reference this post in the Digitalfire Reference Library:

Bentonite, Drying Ceramics Without Cracks, Plasticity

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