Chinese porcelain

DOWNLOAD REFERAT

Preview referat: Chinese porcelain

Porcelain differs from other types of ceramics in its ingredients and in the process by which it is produced. Two common types of ceramics--earthenware and stoneware--are made from a single natural clay, which is then fired (baked). In many cases, the object is coated with a glassy substance called glaze. Firing at a low temperature produces earthenware, a porous material. Earthenware can be made waterproof by glazing. Firing at a high temperature produces stoneware, a hard, heavy material. Stoneware is nonporous without glazing.

Unlike earthenware and stoneware, porcelain is basically made from a mixture of two ingredients--kaolin and petuntse. Kaolin is a pure white clay that forms when the mineral feldspar breaks down. Petuntse is a type of feldspar found only in China. It is ground to a fine powder and mixed with kaolin. This mixture is fired at temperatures from about 2280 _F (1250 _C) to 2640 _F (1450 _C).

At these extreme temperatures, the petuntse vitrifies--that is, it melts together and forms a nonporous, natural glass. The kaolin, which is highly resistant to heat, does not melt and therefore allows the item to hold its shape. The process is complete when the petuntse fuses itself to the kaolin. There are three main kinds of porcelain: (1) hard-paste porcelain, (2) soft-paste porcelain, and (3) bone china. The differences between these types of porcelain are based on the material from which they are made. This material is called the body or paste.

Hard-paste porcelain, which is sometimes called true porcelain or natural porcelain, has always been the model and ideal of porcelain makers. It is the type of porcelain first developed by the Chinese from kaolin and petuntse. « mai multe referate din Diverse