Classical pottery falls into three main categories: earthenware, stoneware, and porcelain. The difference is a matter of what type of clay or clay mixture it is made from; and also the temperature of the ceramic kiln in which it is fired, since the temperature of firing controls both the strength and physical appearance of the pottery. Earthenware is made from naturally occurring clays which can be found all over the world. Usually earthenware is decorated with colorful glazes and designs, and is fired at a relatively low temperatures since high-temperature firing reduces the color of most glazes. Earthenware pottery is quite fragile, and it easily chips and breaks compared with the other pottery types.
Stoneware, by contrast, is a heavy, hard, pottery which is manufactured principally from stoneware clays. Stonewear clay items are fired in ceramic kilns at very high temperatures, which causes the stoneware surface to become glossy. Therefore, it is not really necessary to glaze stonewear. Another advantage of stonewear is that it is both heavier and stronger than earthenware.
The most delicate and purest type of pottery is porcelain, which was invented in China during the Tang dynasty (618 to 907), and was subsequently refined to perfection during the Ming (1368 to 1644 and Qing (1644 to 1912) dynasties. Chinese emperors during the Song dynasty (960 to 1279) founded factories to manufacture porcelain; and in the next few hundred years the secret of porcelain manufacture spread to Korea and Japan. While the secret of porcelain-making was closely guarded by the Chinese, it was discovered independently in Europe in the early 1700's, and soon Europeans created porcelain factories producing such famous wares as Sevres, Meissen, Wedgwood, and Worcester. There are two basic types of porcelain: hard paste, which is fired in a high-temperature ceramic pottery kiln; and soft paste which is fired in lower temperature kilns. Chinaware is an example of soft paste porcelain. Porcelain clay is a mixture of flint, feldspar, and primarily kaolin. Kaolin clay is fine and white, so that porcelain usually fires to a shade of translucent white.
Modern pottery is usually made of polymer clay, which came into wide use in the 1960's. Polymer clay is not clay at all, but rather is manufactured from the same material as PVC tubing (polyvinyl chloride). Unlike the fragility of objects made from natural clays, polymer clay items won't break if dropped. Also polymer clays are fired in the ceramic kiln at much lower temperatures than are natural clays. There are even types of polymer clays which can air dry without needing ceramic kilns at all. Polymer clays allow the creation of pottery of many different colors and translucencies, with embedded metallic or mineral fibers. As with natural clays, polymer clay objects can be hand-decorated with painted, pencil, ink, or chalk drawings before being glazed and fired in the ceramic pottery kiln. The versatility, ease of use, and infinite possibilities for design and manufacture make polymer clays the most widely used clay in the world.
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