Ball clays are normally refractory, none of these are vitrified to any extent. The cone 10R bar is yellow because it is stained by the soluble salts present in the material. These are very typical of what most ball clays look like.
|Materials||OM #4 Ball Clay|
A common problem with dry and fired ceramic. It is evident by the presence of a light or dark colored scum on the dry or fired surface.
During drying, clay particles draw together and shrinkage occurs. During firing the matrix densifies and shrinkage continues. More vitreous bodies shrink more.
In ceramics, porcelains lack plasticity and fire to high density with white, glassy surface. Stonewares are plastic and fire cream to brown and lower density, Porcelaineous stoneware are between these two.