Fire clay is a type of clay which is used in the production of heat resistant clay items, such as the crucibles used in metals manufacturing. This type of clay has a very high fusion and melting point.
Fire clay is a range of refractory clays used in the manufacture of ceramics, especially fire brick. The United States Environmental Protection Agency defines fire clay very generally as a mineral aggregate composed of hydrous silicates of aluminium (Al2O3.2SiO2.2H2O) with or without free silica.
Fire clay can also be used to create fire resistant chimney and flue liners, and fire resistant pads for safety, as seen when a hearth in front of a fireplace is made with fire clay to reduce the risk of fire.
This clay contains high percentages of alumina and silica, with minimal amounts of trace impurities. It tends to be pale to creamy yellow in color, due to the balance of minerals in the clay, although it can also be colored for various applications
Like other clays, this clay is highly malleable in raw form. It can be molded, extruded, shaped by hand, and stamped. Various additives can be mixed in to make it more coarse, and it can be ground to be smoother. Slip and scraps for fire clay manufacturing can also be recycled, as long as they are not fired, and worked into new batches of clay for use. Fire clay also shrinks after it has been molded and during the firing process, which is something to be aware of when working with raw clay.
Because of the abundant supply of fireclay and its comparative cheapness, the refractory bricks made out of it are the most common and extensively used in all places of heat generation, like:
1. in boiler furnaces
2. glass melting furnaces
3. chimney linings
4. pottery kilnsblast furnaces
5. reheating furnaces
Fireclay is classified under acid refractories. Acid refractories are those which are not attacked by acid slag. In blast furnaces, the lining is done almost entirely with fireclay bricks. Pouring refractories like sleeves, nozzles, stoppers and tuyers are made of fireclay.
