Here is the oversize (from Plainsman MSculp) on the four coarsest screens we use to do particle size distributions on clay bodies. There are very few intermediate sizes between the very fine particles of the base body and the coarse particles of the grog and sand. Contrary to what I have thought up until now, lately we have found that this approach makes for greater plasticity, better drying and less water splitting than if the grog and body contain a range of coarse to very fine particles. It also feels smooth 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.