Wire-Cut Extruded Bricks
The clay is mixed with water to a fairly stiff consistency and loaded into an extruding machine, where it is forced under pressure out through a die. The die is machined to a shape and size that is larger than the finished size of the brick, to take account of the extent to which clay will shrink during the
later drying and firing processes. A typical size for the die is 240mm x 125mm.
The clay emerges from the die as a continuous, smooth, brick-shaped column. At this point a decorative finish may be applied to the faces of the brick – a very taut wire is used to slice a thin sliver off the top and both sides in order to produce a ‘wire-drag’ pattern. An alternative finish can be applied by way of textured rollers, or a ‘sandfaced’ finish can be achieved by blasting the column of clay with sand under high pressure.
The column of clay is then cut into single bricks (typically 75mm thick) by means of wires attached to a framework. The wire-cut bricks are then palletized ready for the drying process. Wire-cut extruded bricks are generally solid or perforated and are further characterized by sharp edges or arrises.
Fig. 28 P erforated blocks (engineering).