Clays and Pottery Essay -- Art Molding Papers

ashess and Potteryceramicists, working both on a wheel or building by hand, line three main(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 organic structure is composed of a mixture of clay minerals and other materials such as sand or fine gravel and fluxing agents which affect the color and caryopsis when discharged. Instead of discussing clays solely in terms of their chemical formulae, determined by x-ray diffraction, potters group clays into classes based on more general properties of the broad(a) clay body, such as texture and color. One distinction potters accept is between primary or residual clays, and secondary or aqueous clays. Kaolin is the major primary clay which is exercised in ceramics. The use of the name kaolin for a clay body encompasses more than a body composed of pure kao linite crystals, however, according to Rhodes, the composition of kaolin clays principally fall with in the bounds of kaolinites composition 46%silica, 39% alumina, 13% water (Rhodes p. 47). Kaolinite has the most basic 11 tetrahedral-octahedral clay structure, and maintains a simple and pure composition. So when kaolin is fired along with several(prenominal) 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 not very plastic and thus presents a altercate to the potter in its pure state however, some Kaolins are of aqueous origin (such as those sifted from sands in Florida) and therefore have a smaller particle size which increases the plasticity. Generally though, kaoli... ...In dark colored ball clays containing highly expandible minerals, the increased amount of water in the corpse coming from the interlayer sites can lower the melting point. In addition , the pre-fired color of a clay body may be quite different from the fired color due to the fact that organic material often colorise a wet clay, yet burns away during firing without going a stain.BIBLIOGRAPHYChappell, James. The Potters Complete 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 Art 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.