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The 20cm vase on the left is 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.

This picture has its own page with more detail, click here to see it.
This woman has quickly laid coils of smooth plastic clay on top of each other, in a conical shape. Then she simply begins throwing, centering, compressing and even verticaling the walls on the first pull. Since joining stiffer grogged clay elements, as done in typical hand-building, can be a time-consuming, elaborate process, how can this potter just ignore that?
-The clay is very soft, but very plastic (evident in how the coils are rolled, how the potter dangles the coils like a rope, yet they don’t break, and that she can make such large pieces).
-The coils are rolled on a wet table by a helper, then laid in place while still slip-covered and sticky (it glues them together on contact).
-The piece being made is large and the walls are thick. Asian potters are not averse to doing alot of trimming to thin them later.
-The mere act of applying pressure and thinning the wall also joins the coils.
Watch her do this on the Instagram video link on the home page for this post.
| Articles |
Drying Ceramics Without Cracks
Anything ceramic ware can be dried if it is done slowly and evenly enough. To dry faster optimize the body recipe, ware cross section, drying process and develop a good test to rate drying performance. |
| Glossary |
Plasticity
Plasticity (in ceramics) is a property exhibited by soft clay. Force exerted effects a change in shape and the clay exhibits no tendency to return to the old shape. Elasticity is the opposite. |
| Materials |
Bentonite
Bentonite can make a clay body instantly plastic, only 2-3% can have a big effect. It also suspends slurries so they don't settle out and slows down drying. |
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