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.