stoneware

A type of ceramic midway between pottery and porcelain, made of clay and a fusible stone. It is fired to a point where partial vitrification renders it impervious to liquids, but unlike porcelain it is seldom more than slightly translucent.

Stoneware is a category of clay and a type of pottery distinguished primarily by its firing and maturation temperature (from about 1200°C to 1315 °C). It is usually coloured grey or brownish because of impurities in the clay used for its manufacture, and is normally glazed"

In contrast, earthenware fired at lower temperatures and is not impervious to liquids. Kaolin, or China Clay, which occurs in various parts of the world, has lower content of impurities than many other clays. Vitreous clay bodies can be made at different temperatures ranges, but they are typically fired in the stoneware/porcelain range.

Clay refers to group of minerals that generally exhibit plasticity when mixed with water, and which chemically primarily consist of alumina and silica. Potters refer to combinations of clays mixed with other materials as clay bodies. Different kinds of clay bodies are created by mixing additives, such as feldspar, grog, quartz, flint, many other minerals are used and these can include spodumene, wollastonite to modify natural clays. Natural clays are thereby altered to fire at specific temperatures. Darker clays often contain iron and other metal oxide impurities. The clay used for porcelain and white stoneware clay bodies contain very little of these impurities.

Glaze may be applied to stoneware pottery before a second firing at a different temperature, or a glaze may be applied before a single, raw firing.