Wednesday, September 6, 2017

Varieties of Clay and Glazes

       Pottery is made of various grades of clay, to which sometimes small proportions of fine sand, powdered feldspar or flint are added, the kind and proportion of these ingredients determining the sort of ware. 
       Clays that contain any appreciable quantity of iron turn red when burned, as in the making of brick, and much of the coarsest grade of earthenware is made of this kind of clay. Other varieties turn to a cream color, and others become a reddish-brown. The finest quality of clay used for pottery is known as kaolin and is pure white. Some varieties of clay contain enough sand to make the glaze or enamel, but for most wares this must be added. The glaze is made by different substances for different wares. That of stoneware, such as common jugs and crocks, is made by throwing common salt into the furnace, where it is decomposed and fuses with the clay. Other varieties of stoneware are glazed by a mixture of white lead, flint and glass ground together; while porcelain is glazed by still another composition. 

Glazing your ceramics.

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