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Chemical analysis of the statues reveals that they are made of clay-containing limestone powder mixed with lime plaster made from the same stone.
Plaster can be defined as any plastic material used in a wet
state which becomes hard when dry. In the ancient Near East, early plasters were made from mud or from the rocks gypsum and limestone. Mud plaster requires no heating and can be used almost without alteration as a building material
or for modeling figurines or large-scale statues, but it is not durable. Gypsum plaster, commonly called "plaster of paris," is made by heating gypsum to temperatures slightly above those required to boil water, about
100---200 degrees centigrade.
Plaster made from limestone, by contrast, requires many additional steps and a more sophisticated mastery of technology. The limestone must be heated to a temperature sufficiently high for
it to decompose from calcium carbonate to calcium oxide. For this to happen, temperatures in the range of 600---900 degrees centigrade are needed, depending on the type of limestone. The product is then combined with water. Lime
plaster becomes a durable, water-resistant material when it dries and absorbs carbon dioxide from the air. Lime plaster was used extensively at 'Ain Ghazal for covering walls and floors and for making simple vessels, pendants, and
tokens. Its most important nonarchitectural use was for human-form statues.
The production of lime plaster is closely linked to advances in pyrotechnology, which is the application of heat in manipulating the
properties of materials. The control over high temperatures required to produce lime plaster may have been a key step in the development of ceramic technology. By about 5500 B.C., pottery was produced in kilns at 'Ain Ghazal and
other sites in the vicinity. Later, by about 4000 B.C., Near Eastern metalworkers would also draw on advances in pyrotechnology brought about by the manufacture of lime plaster and pottery.
Ann C. Gunter
Associate Curator of Ancient Near Eastern Art |
