Terracotta

A terra cotta sculpture of Hanuman in India. The reddish colour is due to iron oxide in the source clay. Clays with low iron content can result in paler colours on firing, ranging from white to yellow.
Terra cotta (Latin: "baked earth") is a waterproof ceramic. Its uses include vessels, water & waste water pipes and surface embellishment in building construction. The term is also used to refer to items made out of this material and to its natural, brownish orange color.
Production and properties
An appropriate refined clay "mud" is partially dried and cast, molded, or hand worked into the desired shape. After further thorough drying it is placed in a kiln, or atop combustable material in a pit, and then fired. After pit firing the hot ware is covered with sand to cool, and after kiln firing the kiln is slowly cooled. When unglased, the material will not be waterproof, but it is suitable for in-ground use to carry pressurized water (an archaic use), for garden ware, and sculpture or building decoration in tropical environments, and for oil containers, oil lamps, or ovens. Most other uses such as for table ware, sanitary piping, or building decoration in freezing environments require that the material be glazed. Terra cotta, if uncracked, will ring if lightly struck, but not as brightly as will ware fired at higher temperature, which is called stoneware. The fired material is relatively weak compared to stoneware. Owing to the low firing temperatures it is possible to use lead-containging glases, which although once widely used are now recognized as producing both health and environmental hazzards. (more…)
China
An interview with J. Bjornar Storfjell