- Selecting bricks
A refractory brick is built primarily to withstand high temperature, but will also usually have a low thermal conductivity for greater energy efficiency. Usually dense firebricks are used in applications with extreme mechanical, chemical, or thermal stresses, such as the inside of a kiln or a furnace, which is subject to abrasion from wood, fluxing from ash or slag, and high temperatures.
In the making of firebrick, fireclay is fired in the kiln until it is partly vitrified, and for special purposes may also be glazed.
High-grade fire clays can withstand temperatures of 1775 °C (3227 °F), but to be referred to as a "fire clay" the material must withstand a minimum temperature of 1,515 °C (2,759 °F). Therefore Fire bricks are not needed in braai or fireplaces - a good quality FBX brick will be more than sufficient for the bed of the fireplace, while a standard FBA or NFP brick is sufficient for the sides.