The method adopted will vary according to the nature of the clay used; its water content and type of brick required:

1. Hand-Made: The traditional method of brick making, the clot of clay is rolled in moulding and thrown by hand into a wooden frame mould on a wooden stock, producing individual bricks of various colours and textures. Hand-made bricks usually have a single frog, but may be solid.

2. Soft-Mud: This is an adaptation of the hand-making method. Again, a clay with a high moisture content is used, dropped between two rotating rollers and mechanically thrown into metal moulds which after excess clay is removed, reverse and release the brick, giving a simulated hand-made brick. Soft-Mud bricks generally have a single frog.

3. Semi-Dry: This brick is manufactured using ground clay which is fed into machines and pressed, four times in one cycle and into moulds by heavy hydraulic pressure. The facing bricks are sand-faced or machine textured. These bricks have one frog and are sometimes produced in two or three cells.

4. Stiff Plastic: A similar process to semi-dry, although the clay tends to have an inherently low moisture content such as the shale and deposits. After grinding, extra water is added to the clay dust before delivery to an extrusion pug which forces the clay into moulds, and is then pressed into shape. Sometimes a second pressing is deemed necessary for facing bricks. This method gives a dense, uniform-sized brick.

5. Extruded Wirecuts: Apart from clays with naturally high levels of water, most clays are suitable for this process. Prepared clay is extruded through metal dies to give a long column of clay the correct width and length of the finished bricks. It is then textured by scoring and brushing and/or coloured by spraying. Finally it is cut to the specified guage by a series of wires. Wire-cut bricks do not have frogs, although most contain a variety of perforations, or holes, formed during extrusion.

(Brick Work- History, Technology and Practice: Gerard Lynch)

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