In our own experience we remember that, after having made contracts with the U. S. Government to furnish in one year 17,000,000 brick for the City Hall and other public buildings in Washington City, we seriously contemplated building two Hoffmann kilns on our yard ; but were deterred from so doing because of the uncertainty of being able to haul the brick at all times from our works. Some days we could deliver from 100,000 to 125,000 brick per day to the buildings, the large area of dumping ground around the buildings allowing this, and then for three or four days after heavy rains it would be almost im possible to deliver any brick from the yards because of the inclement weather and impassable condition of the roads.
Our conclusion was, if we built the Hoffmann Kilns and went to the expense of wheeling the brick on barrows from the kilns and hacking them in the yard until such times as they could be rapidly hauled to the buildings during favorable weather, or during periods when there would occur delays in setting the stone-work or the iron-beams of each of the stories, that this loss alone would more than neutralize the saving of fuel and labor resulting from the use of such kilns.
In the United States it is not at all a question of being edu cated up to the use of the Hoffmann or any other form of con tinuous kiln. The real drawback to their use is that the interest on the large capital required to build such kilns, added to cost of wear, tear, depreciation, and repairs, and the in creased cost of setting the brick in them, and the cost of labor for hauling the brick in barrows from the kilns and hacking them in piles and re-delivering them to the carts and wagons, is much greater with us in America than in Europe, where these kilns are in use in large numbers, and where they can be built and operated with profit.
The English as well as the German brick have a volume of about 132 cubic inches (size of English brick 933(43Ax2 inches ; size of German brick g3x43x26 inches). For burning woo ordinary building brick of this size in old fashioned kilns, on an average goo pounds of coal are required, the quantity depending on the nature of the clay as on the quality of the coal. The American brick is of smaller size ; the ordinary building brick, in New York, for instance, having a volume of hardly eighty cubic inches. The quantity of coal required for burning these brick is proportionately less, requir ing only about one ton of coal to burn about 4000 brick of this size, in old-fashioned kilns. One ton of coal costs in America
about $3 ; the coal for burning woo brick in America, there fore, costs about $0.75. According to these figures, the coal for burning woo brick in Europe in old-fashioned kilns cost about $1.80. The market price of brick per woo is about the same in Europe as in America, common building brick, on an average, selling at $6 per woo; therefore, in America, the fuel required for burning in old-fashioned kilns only represents about per cent., while in Europe it represents 30 per cent. of the market price of brick. This difference is caused partly by the difference in the size of the American brick, compared with the European, but is partly offset by the low wages paid in Europe compared with those paid in America.
From the foregoing it is evident that any saving in fuel is of much more importance to the European brickmaker than to the American. It is natural, therefore, that nearly all en deavors to reduce the quantity and cost of fuel required for burning brick have originated in Europe. The Americans, on the other hand, direct their energy and inventive genius chiefly to lessening the cost of the labor in making and handling the brick, especially through the use of labor-saving machinery.
Mr. Guthrie, a master mechanic of Manchester, England, claims to have invented a modification of the Hoffmann kiln in this respect—that the fuel is generated into gas in furnaces on the outside of the apartment in which the brick are contained ; then the brick are burned with the product of combustion, therefore giving a good face brick in all the apartments, wherein the main objection to the Hoffmann kiln is obviated by producing good face brick.
One of these Guthrie kilns is in successful operation at the works of the Columbus Brick and Terra-Cotta Company, of Columbus, Ohio.
There is now no valid patent existing in the United States upon the Hoffmann kiln.
In England and on the Continent of Europe the Hoffmann kilns are commonly built with either twelve or fourteen cham bers, twelve chambers answering all purposes where the brick are thoroughly dried before going into the kiln. But when setting direct from the machine, as in the semi-dry process, not less than fourteen chambers, and even sixteen with some clays, are preferable.