after pit firing the hot ware is covered with sand to cool, and after kiln firing the kiln is slowly cooled. when unglazed, 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. terracotta, 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 weak compared to stoneware.