Not all clays are suitable for molding and firing. The clay must not have the kind of impurities that would cause the body to wrap or crack under heat. It must be moldable, and must retain the shape when it is dry. An area where suitable clay is found often becomes the site of a pottery. By the traditional method, after the clay is dug up it is left exposed to the weather for at least a year, to permit it to disintegrate. Then it is turned over and left another year. In modern commercial practice clay is disintegrate by machine, without aging.
It is then sifted and dried. This essay scrutinizes on how to make pottery. Forming the Object. There are six method of forming dishes and containers from clay of the right consistency to be modeled. They are known commercially as soft-mud processes. These are the pinching, slab construction, coiling, throwing, pressing, and jiggering. Figurines or sculptures made in the round must be hollow, because a very thick piece of clay is apt to blow up in the kiln. Pinching, slab construction, and coiling methods may be used for forming all or part of a sculpture.
If the piece is modeled by building it up out of solid clay, it must be hollowed out. If the cavity is then closed with a clay wall, one or more tiny air holes are needed to accommodate air expansion on the inside of the piece when it is fired. When a clay piece has dried until the body is stiff but still most (a state called “leather hard” or “cheese hard”), some final shaping may be done by turning, another mechanical process such as of turning. Firing. During firing the clay body changes in its physical properties.
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Each body mixture reacts differently to heat, so temperatures may vary widely from those given here. During the early part of firing, water, carbon, and organic matter burn out of the body, leaves pores in the structure of the clay. At about 1, 7500 F vitrification begins; that is, the flux in the clay starts melting and gradually mixing with the silicates, filling the pores with glass. Glazing. The degree of heat required to melt the glaze and fuse it to the body depends on the relationship of the components.
The biscuit firing of fine wares is generally at low heat, and the glost (glaze) firing is at a temperature required for final vitrification of the ware as well as fusion of the glaze. It is possible, however, to fire the biscuit ware to its highest required temperature and to apply a glaze that will fuse at a much lower heat. Decorating. A clay piece may be decorated by adding molded clay to the surface in a relief treatment; by pressing or cutting incised designs into it; or by painting the design with enamel (opaque glaze0, slip, or special pigments.
Moreover, decoration is sometimes applied before the piece is glazed. Such underglaze color, however, is confined to pigments that can withstand the relatively high heat of the glost firing. As a conclusion, pottery is an object made of clay and hardened by heat. The object may range from building brick and drainage tile to fine dinnerware, vases, and figurines. In the broadest sense, pottery may mean all these clay products.
