fire clay

Fire clay is a specific kind of clay used in the manufacture of ceramics, especially fire brick. The fire attribution is given for its refractory characteristics. There are two types of fire clay: flint clay and plastic fire clay.

The raw materials normally used for making fireclay refractories consist of natural argillaceous materials whose mineral composition is represented by the general formula Al₂O₃. The impurities in these raw materials are mainly present in the form of evenly distributed quartz, oxides & hydroxides of iron, hydrohaemetite and magnetite.Organic matters and sulphur compounds also may represent as impurities.

It is resistant to high temperatures, has a fusion point higher than 1,600°C, and therefore it is suitable for lining furnaces, as fire brick, and manufacture of utensils used in the metalworking industries, such as crucibles, saggars, retorts, and glassware. Because of its stability during firing in the kiln, it can be used to make complex items of pottery such as pipes and sanitary ware. Its chemical composition consists of a high percentage of silicon and aluminium oxides, and a low percentage of the oxides of sodium, potassium, and calcium. Unlike conventional brick-making clay, it is mined at depth, usually found as a seatearth associated with coal measures.

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