A cone 10R sculpture clay containing 40% ball clay, 10% kaolin, 10% low fire redart (for color and maturity), some quartz and 25% 20x48 grog. This fine grained base produces a body that feels smoother than it really is and is very plastic. It is even throwable on the wheel.
Grog is a term used in ceramics to describe crushed brick (or other fired ceramic) aggregate that is added to sculpture and structural clays to improve drying properties.
In ceramics, clays with added aggregate are free formed or molding into shapes that are slowly dried and fired in a kiln. The process requires much skill.