Bricks are usually classified in three ways: (a) Manner of moulding; (6) position in kiln; (c) their shape or use.

(a) The manner in which brick is moulded has produced the following terms:

Soft-mud Brick. A brick moulded either by hand or by machine, in which the clay is reduced to mud by adding water.

Stiff-mud Brick. A brick moulded from dry or semi-dry clay. It is moulded by machinery.

Pressed Brick. A brick moulded with semi-dry or dry clay.

Re-pressed Brick. A brick made of soft mud, which, after being partly dried, is subjected to great pressure.

(b) The classification with regard to their position in the kiln applies only to the old method of burning. With the new methods, the quality is nearly uniform throughout the kiln. The three grades taken from the old-style kiln were:

Arch Brick. Bricks forming the sides and top of the arches in which the fire is built are called arch bricks. They are hard, brittle, and weak from being over-burnt.

Body, Cherry, or Hard Brick. Bricks from the interior are called body, cherry, or hard brick, and are of the best quality.

Pale, Salmon, or Soft Brick. Bricks forming the exterior of the kiln are under-burnt, and are called soft, salmon, or pale brick. They are used only for filling, being too weak for ordinary use.

(c) The classification of brick in regard to their use or shape has given rise to the following terms:

Face Brick. Brick that are uniform in size and color and are suitable for the exposed places of buildings.

Sewer Brick. Common hard brick, smooth and regular in form.

Paving Brick. Very hard common vitrified brick, often made of shale. They are larger than the ordinary brick, and are often called paving blocks.

Compass Brick. Brick having four short edges which run radially to an axis. They are used to build circular chimneys.

Voussoir Brick. Brick having four long edges running radially to an axis. They are used in building arches.