Clays and Pottery Essay -- Art Molding Papers

Clays and PotteryCeramicists, working either on a wheel or building by hand, define three chief(prenominal) classes of clay bodies or mixtures earthenware, stoneware, and porcelain. These are divided on the basis of firing temperatures and the character (hardness, vitrification and durability) of the final material. Each clay embody is dispassionate of a mixture of clay minerals and other materials such as sand or fine gravel and fluxing agents which affect the color and texture when fired. Instead of discussing clays completely in terms of their chemical formulae, determined by x-ray diffraction, potters collection clays into classes based on more general properties of the entire clay body, such as texture and color. One distinction potters make is between native or residual clays, and secondary or sedimentary clays. Kaolin is the major primary clay which is used in ceramics. The use of the name terra alba for a clay body encompasses more than a body composed of unmixed k aolinite crystals, however, according to Rhodes, the composition of kaolin clays generally fall with in the bounds of kaolinites composition 46%silica, 39% alumina, 13% water (Rhodes p. 47). Kaolinite has the more or less basic 11 tetrahedral-octahedral clay structure, and maintains a simple and pure composition. So when kaolin is fired along with some silica and feldspar, it forms a highly refractory white solid. As the main ingredient in porcelain, Kaolin comprises, on average, about 50% of a porcelain mixture. Kaolin is non very plastic and thus presents a challenge to the potter in its pure state however, some Kaolins are of sedimentary origin (such as those sifted from sands in Florida) and therefore have a smaller blood cell size which increases the plasticity. Generally though, kaoli... ...In dark colored ball clays containing highly expansive minerals, the increased amount of water in the system coming from the interlayer sites shtup lower the melting point. In additio n, the pre-fired color of a clay body may be quite different from the fired color collect to the fact that organic material often colors a modify clay, yet burns away during firing without leaving a stain.BIBLIOGRAPHYChappell, James. The Potters write out Book of Clay and Glazes. New York Watson-Guptill, 1977. Conrad, John, W. Contemporary Ceramic Formulas. New York Macmillan, 1980. Rhodes, Daniel. Stoneware and Porcelain The blind of High-Fired Pottery. New York Chilton Company, 1959. Velde, Bruce (editor). Origin and Mineralogy of Clays Clays and the Environment. New York Springer, 1995. Velde, Bruce. Introduction to Clay Minerals. New York Chapman and Hall, 1992.