Stoneware is made by firing clay at temperatures high enough for the material to vitrify, or to become glass or a glassy substance. This makes stoneware impervious to light and liquids. In ceramics, stoneware is differentiated from earthenware, clay ware that is not fired at such high temperatures and does not vitrify.
When the body of a stoneware object vitrifies in a kiln, the ingredients melt and begin to fuse, making the piece nonporous. Stoneware does not require a glaze like earthenware does for it to be usable. Stoneware, however, is often glazed for decorative purposes.
Various traditional methods are used to create the body of a stoneware piece before it is fired in the kiln. The process commonly begins by gathering a variety of clays from different sources. The types of clay used dictate the color of the finished stoneware.
Potters use various methods to create the body of a piece before it is fired. One method, perhaps the most common, is to throw the clay in a potter's wheel. The clay can also be liquefied and poured into a mold created by a master mold maker. The clay mixture may also be molded by a ram press. Pieces are sometimes decorated before firing in the kiln.