BRICK-MACHINES. Three classes of machines for the manufacture of bricks, tiles, etc., may be distinguished 1. Soft-clay or sand-molding machines. The clay is taken from the bank, mixed with water, and thoroughly tempered in the machine, and pressed into molds, which are then taken from the machine, and the brick spread on the yard to dry, or put on pallets and dried in racks or artificial driers.
2. Die-melting machines. making brick from tempered clay stiff enough to allow hacking direct from the machine. The clay is ground and tempered by the machine, and is pressed out through a die in the forin mu bar. It is then ent into brick of the desired size by means of strong steel wires. Die-working machines may be divided into two sulcelasses: (a) Auger machines. in whiell the clay is elan intionsly moved out by means of a rotating anger; and (b) plunging machines, in which the clay is pressed out by the reciprocating motion of a plunger, 3. machines, which make brick from finely pulverized dry clay. This last type of machine is adapted to it eomparatively small proportion of clays, and is best snited for the manufacture of pressed brick for the fronts of buildings, As to the relative merits of the various processes of brick-making,, opinions differ widely.
The adherents of the soft-clay process claim that the so-called " soft-mud " brick are not liable to crack or warp in drying. or check in burning; that they are cut easily with the trowel; that the sand surface forms an excellent ground for mortar; that all portions of the brick are equally dense, not having an external shell that is extremely hard and liable to flake off, leaving the porous interior to waste away. It is also claimed that they are much less difficult to burn, and, when well made. and burned, if of good material, have no superior for strength and durability. Against the stiff-mud or wire-cut machines. the soft-clay adher ents urge that the brick produced by them needs repressing; that they are not usually square. aml that the ends are more or less ragged. It is also insisted that the clay being
forced through (lies stiff enough to handle at once, the center of the stream or column moves faster than its surface, and arranges itself in layers or laminations, making the brick very unsuitable for cutting by the mason, and liable to flake.
As against the dry-clay process, it is claimed that it is not possible to construct, a dry-clay machine that will exert the tremendous pressure necessary to be continually given, and last for any reasonable length of time, without making it both clumsy and expensive ; that there is no in density in the product, and that, after baking, the products become open and weak. The advantages claimed for the tempered-clay machines are, that they mix and temper the clay with water as they use it, without any additional handling, or without pre viously drying, rolling, or any other preparation whatever for ordinary clays. taking them just as furnished by Nature. The machines first, after tempering the clay, form it into a parallel-sided bar of the proper width and thickness for a brick, sand the surface, cut this bar in uniform lengths, and then deliver the bricks so molded and sanded in a condition suffi ciently stiff to be immediately wheeled and hacked in the shade or on the drying-car.
The adherents of the stiff-clay machine (-maim that their apparatus does everything between dumping the clay into it and making the bricks ready to hack. The bricks, therefore, do not require to be sun-dried, and hence it is asserted that yards using such machines may run five or six weeks longer in a year than those using soft-clay molding-machines. It is pointed out that. if the soft machine-made or hand-made bricks be not dried enough to hack, in ease of sudden rainy weather. they must necessarily be lost or damaged, The advantages and disad vantages of the different, types of apparatus will he found fully set forth in the trade publica tions of the various brick-machine manufacturers. and need not further be discussed here.