DRY-CLAY BRICK MACHINES.
There has been unquestionably a great advance in recent years in dry-press machines. Those that pressed the clay from one side only are now universally condemned, as it left the side of the brick furthest away from the pressure soft and without strength. There is no doubt, however, but they were the fore runners of our present presses. It was soon discovered that to make both sides of the brick equally hard and strong, it was necessary to make the machine so that both sides of the brick should receive equal pressure. This idea insured both edges strong and sharp. But what about the centre? Ah, "there's the trouble." An ugly granulated central seam running around the middle of the face of the brick was for years the unmistak able mark of a dry-pressed brick, and that is where those man ufacturing by the re-press process made their strongest argu ment. They could point with the finger of pride to their brick having no such ugly defacement, and it cannot be denied that their argument was a just one. The dry process could never hope to compete successfully with the re-pressed method until this fatal objection was overcome. It is safe to predict that machines having this drawback are doomed, and that they will in the immediate future be abandoned. In some machines it is
claimed that this objection has been entirely overcome.
Another important question regarding a dry press is its strength. To make a good ringing brick the particles of clay must be pressed together into as dense a condition as possible. Should it not receive the requisite pressure, the brick will be shaky and fail to have a genuine ring, even when the clay is of an easily vitrifiable character. To withstand this pressure great strength is required in the machine.
The greatest diffieulty that machine men have to contend with is the lamentable lack of knowledge amongst those having charge of the machine after it leaves the shop and goes into actual service. It is an easy matter for a careless attendant to ruin a machine and spoil the reputation of its builder. A fre quent mistake made by those using dry-press machinery is the straining of the machine to its utmost capacity. In pressed brick it is the quality of the product that tells and not the quantity, and very often the former is sacrificed to the latter. Of course, when the dry process is adopted to make common brick, then in that case it is necessary to work up to the limit with little regard to the beauty of the product.