I've carved a little soapstone sculpture, called "playing man" symbol of the way the modern mankind is playing with his toys. I decided to duplicate the soapstone version in ceramic version, for multiplication. I had to create a mold, in several pieces, to get the original, and the ceramic duplicate out. I use plaster of parish, because it soaks the water out of the fluid clay. Pouring the clay into the with rubber straps bounded moldparts, just enough to turn the mold around to be shure the wet clay wil stay glue'd to the whole inside of the mold. When I am satisfied, the whole mold will be filled. Carefully I shake to get rid of any air bubbles. After 15 minutes the clay will be dry enough, on the outside of the clay the moist will have been evaporated to about the thickness I require, and the liquid part of the clay will be poured out. The mold will be kept upside down and after a day drying, a thin wall of the dried clay sculpture the mold can be removed. Now the still moist sculpture has to dry in the air for a week, because when heated in a ceramic kiln, air and fluid can be disastrous. In the meantime, when drying, I can move away parts of the soft clay who are left behind from the moldparts. Very careful sculpting to get the surface in the right shape. After a week or more the scupture is ready for the kiln. I don't have one, so a professional pottery will do this for me. After glazing in the right color and structure, my ceramic sculpture is ready.
