Vitreous china is the ceramic body most toilets, washbasins and bidets are made of. It is cast from a slip of clay, kaolin, feldspar and quartz, glazed, and fired at around 1,200 °C until the body is vitrified.
Product standards for sanitary ware limit its water absorption to 0.5%. A body that takes up so little water does not harbour moisture behind the glaze, which is what makes the material hygienic and durable.