Pottery

C

Decoration

A pot can be decorated before or after firing. When the clay is partially dry and somewhat stiffened (“leather hard”), bits of clay can be pressed into the pot; the body of the vessel can be incised, stamped, or pressed with lines and other patterns; or clay can be cut out and the body pierced. The vessel walls can be smoothed by burnishing, or polishing, so that rough particles are driven inward and the clay particles are aligned in such a way that the vessel surface is shiny and smooth. (Some clays can be polished after firing.) Slip (liquefied clay strained of coarse particles) may be used: The bone-dry (completely dry) or partially dry pot can be dipped into slip of creamy consistency (to which color is sometimes added); or the slip can be brushed on or trailed on with a spouted can or a syringe. Designs can be drawn with a pointed tool that scratches through the slip to reveal the body, a technique known as sgraffito.

D

Glazes

Historically, unglazed pottery has always been more common than glazed pottery. Glaze is a form of glass, consisting basically of glass-forming minerals (silica or boron) combined with stiffeners (such as clay and fluxes) and melting agents (such as lead or soda). In raw form, glaze can be applied either to the unfired pot or after an initial unglazed, or biscuit, firing. The pot is then glaze fired; the glaze ingredients must melt and become glasslike at a temperature that is compatible to that required for the clay. Many kinds of glazes are used. Some heighten the color of the body; others mask it. Alkaline glazes, popular in the Middle East, are shiny and frequently transparent. These glazes are composed mostly of silica (such as sand) and a form of soda (such as nitre). Lead glazes are transparent, with traditional types made of sand fused with sulfide or oxide of lead. These glazes were used on earthenware by Roman, Chinese, and medieval European potters and are still used on European earthenware. Tin glazes, opaque and white, were introduced by medieval Islamic potters and were used for Spanish lusterware, Italian majolica, and European faience and delftware. Eventually the Chinese and Japanese made such glazes for the European market.

Metal oxides give color to glazes. Copper will make a lead glaze turn green and an alkaline glaze turquoise; a reduction kiln will cause the copper to turn red. Iron can produce yellow, brown, gray-green, blue, or, with certain minerals, red. Feldspars (natural rocks of aluminosilicates) are used in stoneware and porcelain glazes because they fuse only at high temperatures. The effects of specific glazes on certain clay bodies depend both on the composition of each and on the potter's control of the glaze kiln.

E

Underglaze and Overglaze Decoration

Pottery can also be painted before and after firing. In Neolithic times, ochers and other earth pigments were used on unglazed ware. Metal oxides used in or under glazes require somewhat higher temperatures in order to fix the colors to the glaze or body—they include copper green, cobalt blue, manganese purple, and antimony yellow. If enamels (fine-ground pigments applied over a fired glaze) are used, the pot must be refired in a muffle (covered, indirect-flame) kiln at low temperatures to fuse the enamel and glaze. Decals and transfer prints (designs printed on paper with oxides and, while wet, transferred to the pot, the paper burning away in the firing) are often used to decorate commercially manufactured pottery. In the 18th century the print plate was hand engraved, but now lithography and photography are used.

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Potters' marks have been used to identify ware in China since the 15th century, and in Europe since the 18th century, and famous pottery marks have always been easily forged. Greek potters and painters signed their work, as is true of a few Islamic potters and most 20th-century potters.

III

East Asia

The leading pottery centers in East Asian history were China, Korea, and Japan. See Japanese Art and Architecture; Chinese Art and Architecture; Korean Art and Architecture.

A

China

In Neolithic China, pottery was made by coil building and then beating the shapes with a paddle; toward the end of the period (2nd millennium bc) vessels were begun using the handbuilt technique, then finished on a wheel. At Gansu, in northwestern China, vessels from the Pan-shan culture, made from finely textured clay and fired to buff or reddish-brown, were brush painted with mineral pigments in designs of strong S-shaped lines converging on circles. They date from 2600 bc. The early Chinese kiln was the simple updraft type; the fire was made below the ware, and vents in the floor allowed the flames and heat to rise. Lung-shan pottery, from the central plains, was wheel made. Chinese Neolithic vessels include a wide variety of shapes—tripods, ewers, urns, cups, amphorae, and deep goblets.

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