ROMSO Cyprus Knowledge Base

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For terracotta or baked earth it refers to clay cooked in the oven or the artifact obtained from it. It is therefore a ceramic material.

History
The art of terracotta dates back to a period between 29,000 and 25,000 BC, when clay vases were cooked with rudimentary methods. The terracotta was the only ceramic technique adopted until it was gradually replaced by porcelain stoneware. In Mesopotamia, Greece, Syria, Sicily and Cyprus, terracotta was used to create votive statuettes, sarcophagi, masks and architectural decorative elements. The technique was first resumed in Republican Rome and then in the Middle Ages, especially in Lombardy and Emilia, where it became the artistic technique of prediletta. In the 16th century, terracotta was also established in northern Germany, while in Italy there were valuable garden ceramic works.

Description
Generally, terracotta bodies show a greater plasticity than most whiteware bodies and therefore are easier to model with the RAM press, roller head or vasal lathe than bone china or porcelain.

For its porosity, the terracotta, with a water absorption of 5-8%, must be glazed to be sealed. The terracotta has a lower mechanical resistance than bone china, porcelain or stoneware, and consequently the articles are commonly made with thicker cross sections, although they are even more easily chinaable.

The darker terracotta, typically orange or red because of a relatively high content of iron oxide, is widely used for flower pots, tiles and some decorative and baked items; it has poor ability to conduct heat, with a thermal conductivity of about 0.8 W/m/K, therefore the food cooking items are well suited for long traditional cooking.

Production

A generic formulation for contemporary terracotta is 25% kaolin, 25% clay, 35% quartz and 15% feldspar.

Modern terracotta can be biscuit (or "bisque") cooked at temperatures between and (from to ) and cooked in gloss (or "smaltato") between 950 and (from to ), the usual practice in factories and in some ceramics from study. Some study ceramists follow the reverse practice, with a low temperature biscuit cooking and a high temperature gloss cooking. The cooking program will be determined by the raw materials used and the desired characteristics of the finished goods.

The terracotta can be produced at cooking temperatures up to () and many clays do not cook successfully above about (). Much of the historical ceramics was cooked around (), providing a large margin of error in which there was no precise way to measure the temperature and conditions very variable within the furnace.

After cooking,