Pottery clays and ceramic clays are all virtually the same; they’re made with a water base and need to be fired in a kiln for vitrification to become permanent and turn red, brown or white when fired. The primary types of art clay are Earthenware and Stoneware. Air-dried modeling clays do not need to be fired in a kiln. They are ceramic clay formulas with an additive to make them harden. Utility and reusability make non-drying, wax and oil-based Plastilina a favorite among students and creative professionals who sketch in 3 dimensions.