BRAZING, brailing. or BRASS- SOLDERENG. The process of uniting two pieces of brass, two pieces of copper. or one of each, by means of a hard solder, partaking more or less of the com position and properties of ordinary brass. (See _ALLOYS.) The edges or parts of metal to he joined are first filed bright, so as to be thor oughly clean; then there is strewn over the gap or crevice a mixture of the solder and borax; and then heat is applied. In brazing, a form of solder appropriate to the kind of work is em ployed, those used for the purpose varying con siderably in composition. (See SOWER.) Most of these solders consist of alloys of copper and zinc, though sometimes tin and other metals are added. The various metals are fused together, allowed to cool, and then filed down to a coarse powder, in Odell the solder is used. The borax is employed to form a glaze over the brightened surfaces, and thus prevent the oxidation of the metal, which would seriously interfere with and even stop the operation. An outward coat ing or layer of charcoal is likewise serviceable it: the exclusion of the air during the brazing of large pieces of metal. Where a very high heat
is required in the process, a little powdered glass is mixed with the borax. The mixture of solder and borax may be applied dry, but it is better to moisten it with water, and to lay it on the tiled surfaces with a spoon. The whole is then gently boated, %Ol•n the water evaporates, and a crust of borax and solder is left. The work may now be strongly heated before the blowpipe, or over a clear tire, and at a bright red heat the solder fuses and the zinc begins to burn with a pale-blue flame. At this stage the solder flushes or becomes liquid enough to per meate the joint or crevice: but should it be tardy in acting thus, several slight taps will insure the proper result, The whole is now cooled, and toward the close of this process the articles may be introduced into cold water for inure rapid reduction in temperature. Pieces of metal which have undergone the process of braz ing are so firmly united that they may be rolled and re-rolled without the parts yielding.