is dug from the ground and left to break down by frost action over the
winter. In the spring it is taken from the pile and mixed as necessary with
other ingredients such as sand, other clays, lime or clinker. It is then
ground in a pugmill.
mould a brick, the maker first sands the mould to prevent the clay from
sticking. A lump, of clay is thrown into the mould and pressed into the
corners. The excess clay is then taken off the top with a 'strike'.
green brick, which is wet but firm, is turned out onto a thin board for
loading on the barrow.
barrow-load of green bricks is then taken to a drying 'hack'. The bricks are
stacked up in a long line, either in the open (covered with straw, or
movable 'hack covers') or in a drying shed.
dry, the bricks are placed in a kiln or clamp. A kiln is heated by
continually burning fuel in the firing hearths, whereas in a clamp the
burning material is included within the bricks themselves in the form of
clinker in the clay.
Firing the kiln or clamp takes several days. After a gradual start to drive
off moisture, the temperature is increased to about 1,100°C, until the
bricks are all burnt. The kiln or clamp is then allowed to cool before the
bricks are unstacked ready for use.