Q: I want to make a life-sized bust in ceramic clay and fire it. Are there
any special precautions I have to take?
A: If you intend to fire this bust the basic problem is creating a structure
that allows the heads to remain hollow, while providing some support. This
cannot be altogether rigid, or the clay will crack as it shrinks. The clay
skin should not be more than an inch in thickness, or it will tend to explode
in the firing process due to the expansion of retained water. Make sure
that you do not create an unvented void in the piece, since expanding air
can have the same effect.
One approach is to make an open structure of clay slabs that are strong
enough to support the outer skin, but are weakened sufficiently so as not
to resist as it contracts. I have seen this technique used for making large
sculpture and even ceramic furniture. Alternatively, you can use a combustible
material such as crumpled paper or shredded wood (excelsior) which forms
a non-rigid core. This can be removed prior to firing or left in to burn
out in the kiln.
Andrew Werby
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