DRYING THE BRICK.
The different methods of drying brick may be classed as fol lows : First, when brick are spread out on the ground to be dried by sunshine. Second, the shed system, where stiff-mud brick are hacked under sheds and dried by natural air-currents ; soft-mud bricks are dried on the same principle by the use of racks and pallets. Third, by artificial heat—the first and oldest method of employing artificial heat for desiccating brick being to dry them by laying or hacking them on a hot floor. This is known as a hot floor or flue dryer. This floor is heated by a system of flues passing under it, from furnaces at one end to stack at the other end. The second method by the use of arti ficial heat is the tunnel system, where brick are put on cars, either hacked on the bottom of car or resting on hacking pal lets. The cars are passed through heated tunnels, and when dry are carried direct to the kiln on the cars. Of this class there are several kinds. Another plan is to place them in cup. boards, and drive hot air through them by means of blowers which supply heat to the cupboards through hot-air pipes.
The disadvantages of drying brick in the sun are that they are exposed to rain and frost, and the percentage of brick dam aged and lost will average 15 per cent. Again, there is no cer tainty about the supply of sunshine ; while it is furnished without price, it is also furnished without regularity, and sometimes, for two weeks at a time, no brick are dried ; hence, the brick maker who depends on this process of drying has an uncertain output indeed. Still there is much more certainty about the output than there is about the number he may put into the kiln. There are only six months in the year during which they can be dried in this way, and only a part of this time is available. Where brick are made in great quantities, a large area for dry ing the brick is needed, as it must contain nearly a week's production. This necessitates the moving of the brick long distances from machine to yard and from yard to kilns, and also the handling of large quantities of lumber to protect the brick, which requires a good deal of labor, and destroys in a season many thousand feet of the very best lumber. The advantages of sheds over the sunshine process, are there is no loss by storm, and no lumber to handle.
The pallet system is advantageous with soft-mud brick, for they can be dumped from the moulds at the machine. This prevents sticking in the moulds, and when placed on pallets they can be put in racks one tier above another, and a large quantity can be stored in a comparatively small space, and when the racks are provided with projecting roofs or canvas sides, they save the brick from damage by rain, so that shed drying and the rack and pallet system are great improvements over the old methods, but are open otherwise to the same ob jections that the sunshine method is, that brick cannot be dried in damp weather.
The general advantages of artificial drying over natural are many, without reference to the advantages of one mode of artificial drying over another mode of artificial drying. With an artificial dryer and a machine capable of producing 25,000 brick per day, a brick-maker can make six millions to seven millions per year. To dry without artificial heat it would re quire two machines of 25,00o capacity to produce the same number of brick ilia year. - Now, with one-half the labor, tools, power, and consequently little more than half the capital, he produces the same results. He then gives his employes steady work, and in this way obtains and retains a better class of men for perhaps less wages. There is much less worry and respon sibility ; he has no anxiety about a storm coming in the night and damaging or destroying his day's products, or perhaps a week's labor may be swept away, and his yard left in such a condition that he can make no more brick for several days. With proper drying facilities the manufacturer can contract to sell his brick for future delivery, knowing he can fill his orders without being compelled to carry a large stock ; instead of having to make brick in the autumn for the spring market, he can sell his entire product up to the end of the year, and begin in January or February and have brick ready for the early spring market.
In partially drying machine-made brick for repressing, soft mud brick are usually carried from the brick-machine to the yard or drying-shed, where they remain until they are in con dition for re-pressing.
Just here many have their greatest difficulty, as the brick will dry more rapidly on the surface than inside, especially the angles and corners, and by the time the centre of the brick is stiff enough to stand handling, the surface is too hard to re press. What is needed at this point is to equalize the moisture that remains throughout the brick by taking the brick and setting them in close hacks; then cover them with canvas or old carpets that have been moistened, let them remain a few hours, when uncovered they are ready to re-press. Part of the moisture in the centre has come to the surface, and every part is ready for pressure and handling.
After being re-pressed the soft-mud made brick are often finally dried on a hot floor by setting them on end, and in this way it is possible to finally dry them in three days. To set them on end without injury they must be pressed quite stiff— the safer way is to place them on edge or on their flat side to dry. Where the hot floor is not used, the brick are often placed on smooth pallets to dry.
Semi-plastic-clay brick may be pressed direct from the machine, as they are then sufficiently dry to be handled from the re-press without injury.