Fine fireclay is a sanitary-ware body that contains chamotte, clay that has already been fired and ground. The chamotte reduces shrinkage and warping, so large, flat pieces such as wide washbasins, shower trays and kitchen sinks keep their shape in the kiln.
The body is more porous than vitreous china. The glaze therefore has to cover every exposed surface, and chipped glaze should be repaired rather than left.