In the fire-brick factories of St. Louis, Mo., there is in use a somewhat different method from the above. There the clay or mud is made very stiff and moulded direct into the press-box of a press, and when it leaves the press is finished ready for drying. Of course a man cannot make so many brick, not over about half the quantity ; but the saving of so much un necessary handling, and the saving in room required, make a decided reduction in the cost of the brick. This, of course, is confined to nine-inch work, or at most, to 13 Xx6 furnace blocks. All large shape and special work is of course made in wooden moulds by hand, and the writer is inclined to think from practical experience that there is hardly likely to be any change in the method of making this class of work. In the various forms of nine-inch work, however, which forms the staple of the fire-brick business, machinery has been introduced which seems likely to effect a revolution in the trade. This is emphatically a mechanical age, and its influence has long been felt and ac knowledged by every other department of clay manufacture. Fire-brick makers, however, have been content to still go on in the old humdrum way, and the moulder laboriously makes his clot, or warp, or pone, and whacks it into the mould. Fire brick makers, as a rule, have settled down to the idea that they will never be made any other way as long as the world stands, and few of them will even listen to the idea of making by machine. In fact, there has always been a decided notion that they cannot be made except by hand moulding. But all this is no argument, and it should not be forgotten that similar opinions have been held upon many other things in regard to the adoption of machinery. It must be confessed that many failures and few successes have attended all attempts at machine-made fire-brick in the past. But every failure, if carefully observed, is one step nearer to success.
Mr. Joseph Cowen, of Newcastle, England, says that in the North of England (Northumberland and Durham) attempts have been repeatedly made to produce fire-brick by machinery, yet without success ; whereas in Wales such an application has succeeded, owing, it is suggested, to the Welsh clay differing in quality from that of the North ; and in his opinion fire-brick will continue to be made by hand. 1Machine-made brick, he says, are always more compact than those made in the old way, and this he considers a defect. Mr. Cowen here prob ably strikes the keynote to the cause of most of the past fail ures in previous efforts to make first-class fire-brick by machinery.
The question of moulding without pressing, as in England, and that of moulding and pressing, as practiced in this country, is worthy of consideration, hence the writer will give particulars of the English process and reasons why.
The clay is prepared as stiff as it can be worked up by the hand of the moulder into a solid warp or ball ready for the mould. As he raises it from the table it will be found to be
regular in form, the shape of the mould, only smaller, so that it will go in quite clear and spread out to the sides and ends of the mould. The moulder raises it up well and throws it into the mould quickly and with force. The moulds of one brick each are cast of brass, light and thin, with stronger flange round the wearing parts, that is, the top and bottom. The moulds being open, between these two flanges light oak sides or strips are placed, running about two inches past each end, forming lugs for the off-bearers to handle them. These ends are rounded off, and a small iron bolt is riveted through each pair of ends, making the whole tight and firm. The moulder will, after delivering the clay into the mould, strike off any sur plus clay, sprinkle on a little water, then again run his striker or planing-board twice over the surface, giving it a perfectly smooth and finished appearance. A boy then takes the mould from the table and delivers the brick on a pallet which is placed on a small bench by his side. The second boy or runner comes up to the bench with pallet in each hand, lays one on the bench and places the other on top of the brick, picking up the two pallets with the brick between, which at the same time presses down any bead left on the brick in coming from the mould ; he runs off with it and places it on edge, the same as when taken from the press.
The mould being of perfectly smooth brass requires neither sand, water nor oil, and the ball of clay being properly pre pared by hand and well thrown in, the brick comes out with a perfectly smooth skin, as from the press.
In this way of moulding the cost is exactly the same as moulding and re-pressing in this country. In the former a man and two boys mould 2,000 brick for a day's work, in the latter a man and two boys mould 2,000 and press them. It may be asked, Where, then, is the advantage? It is in the uniformity of the density of the body and the perfect regularity in thick ness, a matter of great importance in fire-brick manufacture and a regular cause of complaint where brick are re-pressed. This irregularity of thickness in re-pressing is principally caused from the brick when moulded and placed on a dry-floor which is hotter in some places than in others, and also that the brick last made have been on the floor longer than those first made be fore going to the press. Brick to be regular in thickness must all be of the same consistency or stiffness when they are placed in the press box, which is almost an impossibility ; hence the advantage of the former system.
In the St. Louis, Mo., district the method of moulding is dif ferent from either of those which have been described. There no moulds are used. The clay is made very stiff and moulded in the press-box of a hand-press at the same time, and put out on the hot floor to dry without any immediate stiffening.