Today bricks are made by machinery from a clay body containing much less water. The two main processes are pressing and extrusion . Once formed the bricks may be surface coloured with metal oxides, such as manganese, or other decorative effects obtained. The bricks are then dried, usually in a drying oven which may utilise waste heat from the kiln. Firing to about 1000oC takes place in a kiln fuelled with wood, coal, oil or gas.
Natural gas is used by the vast majority of brick makers today.
Continuous tunnel kilns are most common today and are much more energy efficient than intermittent kilns. They produce bricks of a very consistent quality. Bricks fired to a higher temperature tend to be darker in colour and more dense and hence stronger than those fired to a lower temperature. The compressive strength of clay bricks made in Australia is between 20-80 MPa. This strength is, in a sense, wasted when bricks are not used in load bearing situations.