bricks, and, being subjected to low steam pressure in the cylinder, the condensing water in one case slacks the lime, developing heat which aids in the hardening process. The second process is identical, except that, instead of condensing steam, water is injected to slack the lime. The Neefgen patents cover a method of hardening sand-lime bricks by subjection for five days to a moist atmosphere heated to 100° C. and subsequent exposure to the open air. These are all mere details and involve alleged improvements which may be advantageous under certain conditions, but are not essential. The evidence is cumulative and convincing to show that sand-lime bricks and building stone can be and are made successfully in Germany without recourse to any patented process. Messrs. Röhrig & Koenig, the eminent machine builders at Magdeburg, state in a recent letter: It can therefore be asserted that to-day not one of all the lime-sand-stone factories works according to any system whatever, although in the first years of the industry large sums were spent for licenses. It was found in each case that it was impossible in practice to work according to the specifications of the patents, and such sweeping changes had to be made that nothing useful remained of the patented processes. Messrs. Brück, Kretschel & Co., of Osnabrück, also builders of machinery for this and other purposes, declare in their catalogue: * * * It is now proved beyond all doubt that in the production of calcareous-sand bricks it is unnecessary to have recourse to patented methods. Patents have been granted for entirely unimportant improvements in the methods of production, and which, instead of proving valuable, gave rise to much trouble and complicated the process. Furthermore, this important industry has been injured by the way in which some of the methods of manufacture have been puffed up, since the promoters of a particular process did not hesitate to publish low costs of production which could not at all times be verified, but soon proved entirely false when actual working operations were begun. Mr. Amandus Kahl, of Hamburg, who has also been cited as a prominent and experienced builder of machinery, says: Without the use of any patent, lime-sand stone can be made equally well. The points of principal importance in this manufacture are not patented and can not be. Few of the patents are of any value. All this does not, however, alter the fact that some of the highly improved machines which are made and used in Germany to-day for the various operations in manufacturing sand-lime bricks and stone do include special improved parts and features which are covered by patents granted in this and other countries. But in such cases the patent is owned by the maker of the machine, and the use and advantage of it, whatever they may be, are sold to each purchaser of such machine. It is not, however, necessary, or apparently advisable, to purchase any patented method or system to enable a manufacturer to make calcareous-sand stone and brick of the best quality. The conditions of success are pure, sharp sand and fresh, clean lime in large quantities, at the lowest practicable cost, cheap fuel, and easy, cheap transportation for the finished product to a ready market. These conditions are best met where a manufacturer can build his plant in close proximity to the sand bed and make his own lime from conveniently derived limestone. BERLIN, GERMANY, August 7, 1903. FRANK H. MASON, Consul-General. |