BRICK, a kind of factitious stone, made of argilla ccous earth, formed in moulds, and baked in kilns, or dried in the sun.
This substance is now in very common use as a ma terial for building; and its importance, in many cases, as a substitute for stone, is generally acknowledged. It is lighter than stone, and not so subject to attract damp and moisture; and from the quantities that are now made in Britain, its manufacture has become a con siderable object of revenue to the state.
The art of brick making consists chiefly in the pre paring and tempering of the clay, and in the burning of the bricks; and as the quality of the ware depends very much upon the right performance of these opera tions. we shall present our readers with a short sketch of the general process of this manufacture. The earth proper for making bricks is of a clayey loam, neither abounding too much in argillaceous matter, which causes it to shrink in the drying, nor in sand, which renders the ware heavy and brittle. As the earth, be fore it is wrought, is generally brittle and full of extra neous matter, it should be dug two or three years be fore it is used. that, by being exposed to the action of the atmosphere, it may be sufficiently mellowed and pulverised, and thus facilitate the operation of temper ing. At any rate, it should always have one winter's frost; but the longer it lies exposed, and the more it is turned over and wrought with the spade, the better will be the bricks.
The tempering of the clay is performed by the tread ing of men or oxen, and in sonic places by means of a clay mill. If the operation be performed by treading, which is the common war, the earth is thrown into shallow pits, where it is wrought and incorporated to gether until it is formed into a homogeneous paste, which is facilitated by adding now and then small quan tities of water; but the less water that is used, the sub stance of the clay will be more tough and gluey, and con sequently the bricks will be smoother and more solid. This operation is the most laborious part of tbe pro cess; but it is of essential importance, and therefore ought to be done well; for it is to the negligence of the manufacturers in this respect, that we are to attribute the bad quality of our modern bricks, NI bleb -re often light and spongy, and full of cracks. NVIiereas, it the clay be properly tempered, they are hard, ponderous, and durable; much stronger and better fitted for every kind of building, than those made in the common way.
This will appear very evident from the following expe riment of M. Gallon. Having taken a quantity of brick earth tempt in the usual way, he let it remain ex posed to the air for seven hours, and then caused it to be moistened and beaten for the space of half an hour : the next morning the operation was repeated ; and in the afternoon the clay was again beaten for fifteen mi nutes more; making the whole additional labour an hour and a quarter. The bricks made of this earth be ing dried in the air for thirteen days, and burned along with the rest without any particular precautions, were found to be not only heavier than common bricks, but also very different in strength ; for on placing their centre on a sharp edge, and loading both the ends, Alr Gallon found, that while it took a weight of 65 lb. at each end to break them, other bricks were broken by the weight of only 35 lb. The improvement in the quality of the article thus far exceeds the additional labour ; and none would hesitate to give an additional price, since both the value and the comfort of our dwellings depend so much on the quality of the materials of which they arc constructed.
The next part of the process is the moulding of the bricks. This is a very simple operation, and requires very little skill, unless it be to make the greatest num ber in the shortest time; and the day's labour•of a han dy workman, employed from five in the morning until eight at night, is calculated at about 5000. The clay is brought to the moulder's bench in lumps some what larger than will fit the mould. The moulder, having dipt his mould into dry sand, works the clay into it, and with a flat smooth stick strikes off the superfluous earth. The bricks are then carried to the hack, and there ranged with great regularity one above the other, a little diagonally, in order to give a free passage to the air. The hacks are usually made eight bricks high; and wide enough for two bricks to he placed edgewise across, with a passage between the heads of each brick. In fine weather a few days are sufficient to make them dry enough to be shifted; which is done by turning them, and resetting them more open; and in six or eight days more they are ready for the fire.