Kaolin is one of a number of alumino-silicate clays consumed by the refractory industry.  These clays have alumina (Al₂O₃) contents of around 20% up to 45.9% for theoretically pure kaolin.  In general terms, the higher the alumina content the more refractory the material.  

Refractories are heat resistant materials used to line high temperature furnaces, reactors and other processing units.  The most important characteristic of refractories is their ability to maintain their shape and strength at high temperatures under mechanical stress and attack by a variety of hot gases, liquids and molten or liquid materials.

Refractories are divided into acid and basic categories.  The term “basic” or “acid” refers to the environment in which the refractory is used rather than its composition.  The distinction between the two types of refractories originated in the steel industry where different products were used to handle basic or acid slags.  Open hearth and electric arc furnaces can use either acid or basic refractories but only basic refractories are used in basic steelmaking processes.  In the glass and ceramic industries, operating conditions are generally acidic.  Both acidic and basic refractories are used in the non-ferrous metal industry.

Acid refractories are manufactured from aluminosilicates and silica but those with high alumina contents are considered to be essentially neutral.  This type of refractory can remove any phosphorus present in a furnace, which can be detrimental to the quality of iron and steel produced.  Basic refractories can be manufactured from natural or synthetic magnesite, chromite, dolomite and forsterite.  

Refractories can be further divided in to bricks and monolithics.  Refractory bricks are classified according to physical dimensions.  The standard size for refractory bricks is 23cm x 11.4cm x 6.4cm, also known as 9 inch brick.  All other bricks are referred to special shapes and are produced for use in specific applications.  Monolithics are made of the same materials as refractory bricks but until recently were used mainly to seal structures made from refractory bricks preventing slag, vapour and flame penetration.  Monolithics are further subdivided by application into mortars, ramming mixes, gunning mixes and castables.  These are then divided by their chemical composition into fireclay, mullite, high alumina, silica-magnesia, magnesite-chrome, chrome, alumina-chrome, alumina-graphite, zircon and alumina-zirconia-silica (AZS).

The iron and steel industry is the largest market for refractories.  Technological advances have improved the quality of refractories, primarily because consumers require ever-longer lifespans from products.  Increased resistance to wear and thermal shock increases the lifespan of a refractory product and reduces the number of times a furnace has to be taken out of production for the lining and refractory components to be replaced.  Consumption of refractory raw materials has also been reduced because of these technological improvements.