The installation of a manufacture of this kind requires plenty of room, for the bricks, which are laid singly on the ground, must have the time to harden before being put into hacks. The first thing to be done is to choose a situation. A piece of ground is chosen, near the heap of clay which has already been weathered, and on a slope, in order that the rainwater may run off easily. This water, collected in a pool, may be used to moisten the clay. The ground is afterwards scraped with a shovel to remove inequalities, and is then smoothed by means of a scraper (Fig. 84b), a tool composed of a board of about 0.50 metres long, and 0.10 to 0.15 metres broad,furnished with a handle placed at right angles to the board.
We have mentioned those used in preparing the clay; for moulding there are required: a special square table, a sandbox, also called a "minette," two double moulds, a "plane" or strike, a bucket or tub, and finally some wheelbarrows for transporting the clay from the heap to the moulding-table, and the bricks from the ground to the hack.
Fig. 83. Sand-box.
Fig. 84. Moulding- table.
Fig. 84a. Double Mould.
Fig. 84b. Scraper.
Fig. 85. Bricks laid on the ground.
The moulding-table (Fig. 84) has four legs and is about 0.80 metres high, and has about one square metre of surface. At one corner a part of the board has been cut off, of slightly larger dimensions than the mould laid flat. This portion is covered with a plate of thin iron to prevent wearing away, for it is here that the moulding is done.
This protected piece of wood is fixed to the upright of the table by means of two hinges on which it turns; and in order that it may lie flat in its normal position, a chain is fixed to it, with a mass as counterpoise - generally a stone.
The sand-box or "minette" (Fig. 83) is a square wooden tray placed at the same height as the table, and about 0.20 metres deep. It is filled with fine and very dry sand, or, more economically still, with crushed and sifted terra-cotta.
The mould (Fig. 84a) is double and made of beech-wood of the best quality of about 1 centimetre thick; it is covered at the edges with plates of sheet-iron to prevent wear. Sometimes it is furnished with a bottom, to make one of the faces of the brick smoother.
The use of the single mould is a waste of time, as the moulder can easily take at one time the quantity of clay required for two bricks. The dimensions of the moulds must be calculated according to the amount of contraction which the clay will undergo in drying and firing.
If the brick is to be stamped, the mould must be higher than for an ordinary brick. Contraction is generally estimated at from 5 to 10 per cent. - that is to say, in order to have a brick 0.22 x 0.105 x 0.05 after firing, a mould of about 0.23 x 0.115 x 0.052 must be used, contraction acting principally on the breadth of the brick on account of its position in firing. But the contraction of clays, is very variable, and experience alone can guide us.
The "plane" or strike (Fig. 84) is a plain oak board, well finished, and having one end shaped as a handle. Sometimes a steel blade is used.