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TYPES OF WARES
Pottery comprises three distinctive types of wares. The first type, earthenware, has been made following virtually the same techniques since ancient times; only in the modern era has mass production brought changes in materials and methods. Earthenware is basically composed of clay--often blended clays--and baked hard, the degree of hardness depending on the intensity of the heat. After the invention of glazing, earthenwares were coated with glaze to render them waterproof; sometimes glaze was applied decoratively. It was found that, when fired at great heat, the clay body became nonporous. This second type of pottery, called stoneware, came to be preferred for domestic use. The third type of pottery is a Chinese invention that appeared when feldspathic material in a fusible state was incorporated in a stoneware composition. The ancient Chinese called decayed feldspar kaolin (meaning "high place," where it was originally found); this substance is known in the West as china clay. Petuntse, or china stone, a less decayed, more fusible feldspathic material, was also used in Chinese porcelain; it forms a white cement that binds together the particles of less fusible kaolin. Significantly, the Chinese have never felt that high-quality porcelain must be either translucent or white. Two types of porcelain evolved: "true" porcelain, consisting of a kaolin hard-paste body, extremely glassy and smooth, produced by high temperature firing, and soft porcelain, invariably translucent and lead glazed, produced from a composition of ground glass and other ingredients including white clay and fired at a low temperature. The latter was widely produced by 18th-century European potters. It is believed that porcelain was first made by Chinese potters toward the end of the Han period (206 BC-AD 220), when pottery generally became more refined in body, form, and decoration. The Chinese made early vitreous wares (protoporcelain) before they developed their white vitreous ware (true porcelain) that was later so much admired by Europeans. Regardless of time or place, basic pottery techniques have varied little except in ancient America, where the potters wheel was unknown. Among the requisites of success are correct composition of the clay body by using balanced materials; skill in shaping the wet clay on the wheel or pressing it into molds; and, most important, firing at the correct temperature. The last operation depends vitally on the experience, judgment, and technical skill of the potter. DECORATING TECHNIQUES In the course of their long history potters have used many decorating techniques. Among the earliest, impressing and incising of wares are still favored. Ancient potters in Egypt, Mesopotamia, Greece, northern India, and the high regions of Central Asia (where primitive terra-cotta figures associated with religious cults were produced) frequently decorated wares with impressed or incised designs. A notable incising technique developed more recently was that of Korean potters working in the Koryo period (918-1392). These artisans began by ornamenting their celadon wares with delicately incised and impressed patterns and later developed elaborate inlaying by filling incised lines with colored slip (semiliquid clay). Black and white slip was used most effectively for inlaying colored porcelains. Decoration of this sort generally depends more on the skill of the artisan than on the complexity of the tools being used. An especially popular type of decoration involved the sgraffito, or scratched technique used by Italian potters before the 15th century. This technique, which is thought to have reached Italy from the Near East, was probably derived from China, where it was first used during the Song (Sung) dynasty (960-1279). By the 16th century Italian potters working mainly in Padua and Bologna had developed great skill in sgraffito, which entailed the incising of designs on red or buff earthenware that had been coated with ordinary transparent lead glaze, usually toned yellow or, sometimes, brown, copper, or green. After firing, the wares were dipped into white clay slip so that a dark pattern could be cut on the surface. By cutting through the white slip, the artist produced a design on the exposed red or buff body. Pigments were also sometimes applied. After a further coating of lead glaze the ware was fired a second time.
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