RECENT PROGRESS MADE IN BURNING BRICK.
The progress recently made in burning brick has been almost as rapid as the improvements in the machinery, even if it has not reached the same perfection. We are indebted to Wingard, Morrison, Eudaly, and Melcher for their square-top kilns, and for superseding the old methods of burning with wood, which destroyed the brick in the arches, and was expensive. Owing to the scarcity of wood in many localities its use had to be abandoned. It would be almost impossible to burn all our yearly product of brick with wood now, as it would require annually 2,500,000 cords. This wood, piled four feet high and four feet wide, would reach over 3,700 miles in length. The round, or down-draft kiln, has merits for face or hard brick, but for large works the continuous kiln for burning common brick is the most saving. Mr. Frederick Hoffman, of Berlin, is the inventor of this kind of kiln. They are in general use in Europe, over too of them being in England, and 250 on the Continent. Mr. Hoffman writes to Mr. B. W. Blair, of Cincin nati, Ohio, from whose address, delivered at the second annual meeting of the National Brick Manufacturers' Association, I have several times quoted in this work : " The principal advan tage of my kiln is saving of coal.. Ordinary brick kilns require about one ton of coal to 4,00o brick. Here in Germany about three-fourths of all brick made are burned in my kilns. In England the Royal Admiralty, as well as several railroad companies, have adopted them. The Russian government have adopted them at the fortresses of Brest-Litewsk," etc. We believe there are continuous kilns at Omaha, Neb., and Columbus, Ohio, but of their merits we are not thoroughly familiar. The cost of burning brick in the Hoffman kiln, where the cost of coal does not exceed $2.5o per ton, is about thirty five cents per thousand. It is possible to melt the brick quicker in a Hoffman kiln than in any other, unless an experi enced foreman is in charge. Natural gas, where it can be obtained, exceeds all other methods of burning. Experiments are being made with oil for burning brick, and also with arti ficial gas generated at the kiln. All attention is turned to burning now, and we may expect great improvements within a few years. What is now required is greater economy of fuel in burning brick, more perfect combustion, and even in many of the present improved plans there is too much waste of fuel and loss of brick from " spaulding" and melting together.
Even in the old open-top kilns, which by this time should be properly understood, there is great loss caused by improper firing; only enough coal should be thrown in at each firing to make a light coating all over the grate surface, say four dirt shovels full ; the thickness of burning coke on the grates should not exceed four or five inches, and the grates be kept so as to show a bright light in the ash-pit at all times ; and to save grates, hot coals should never be allowed to remain in the ash pit.
There should be more space at the top for heat to escape while water-smoking than when settling a kiln, as the draft is less strong at first for the reason that the brick are cold and damp ; as they become heated and throw off more heat, the draft be comes stronger, then the space on top must be reduced. This can be accomplished in an open-top kiln by the platting, the bottom platting being laid in strings one inch apart, the top platting crosswise of bottom platting and close together. While water-smoking a few rows of the top platting are raised, then as the heat begins to escape too rapidly, these are put in their place; another way is to lay top platting, leaving some space between them, then when ready to tighten they are forced together and other brick put in the spaces. The former plan is preferable, as it is less work to close up the top, and the heat can be controlled better while water-smoking with the first plan. In firing any of the forms of furnace kilns ordinarily immense volumes of black smoke continue to roll off for ten or fifteen minutes after firing, and when the kilns are so burned as to prevent the emission of the black smoke there results a material saving in the cost of burning, and it involves the ques tion of water-smoking. Water-smoke is a product of heat coming in contact with the combined water that, is in the material, the brick. If the brick be exposed to the sun, on hot days, like we have in July, and are allowed to stay there two or three days, covering them up over night to keep away the dew, then putting them in the kiln, they are not water-smoked. Why ? Because all the combined water that lies between the little molecules of the clay does not evaporate in the atmosphere. When these are warmed up to 212 degrees then it becomes steam ; and when water is turned into steam it increases in volume 1700 times, and one inch of water is 1700 inches of steam. This is one of the reasons why when we begin to burn this brick the brick begins to swell. Now, this water-smoke, as we call it, is turned into steam and passes away. If we un dertake to raise the steam by putting in coal, it sends the car bon out of the top of the kiln in smoke and results in loss.