Production and Properties
An appropriate refined clay is shaped into the desired shape. After drying it is placed in a kiln, or atop combustible material in a pit, and then fired. The typical firing temperature is around 1000°C. The iron content gives the fired body a yellow, orange, red, "terracotta", pink, grey or brown color. Fired terracotta is not watertight, but surface-burnishing the body before firing can decrease its porousness and a layer of glaze can make it watertight. It is suitable for in-ground use to carry pressurized water (an archaic use), for garden ware or building decoration in tropical environments, and for oil containers, oil lamps, or ovens. Most other uses such as for tableware, sanitary piping, or building decoration in freezing environments require that the material be glazed. Terracotta, if uncracked, will ring if lightly struck. Some types of terracotta are created from body that includes recycled terracotta ("grog").
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