Brass-plate rolling

—At Hegermühl there are two re-heating or annealing furnaces, one larger, 18 feet long, and another smaller, 8 1 ⁄ 2 ; the hot chamber is separated from the fire place by iron beams, in such a way that the bra castings are played upon by the flames on both their sides. After each pa age through the laminating pre (rolls) they are heated anew, then cooled and laminated afresh, till they have reached the proper length. The plates are besmeared with grease before rolling. IMG:4147767755307473660_illo0168b.png:Furnace Fig. 166. shows the ground plan of the furnace and its railway; fig. 167. the cro section; and fig. 168. the section lengthwise; a a , the iron way bars or rails upon the floor of the foundry, for enabling the wheels of the waggon-frame to move readily backwards and forwards; b b , the two grates; c c , the ash pits; d d , the fire beams; e e e , vents in the roof of the hot chamber f ; g g , two plates for shutting the hot chamber; h , the flue; i , the chimney. After the rolling, the sheets covered with a black oxide of copper, are plunged into a mother water of the alum works for a few minutes, then washed in clean water, and lastly, smeared with oil and scraped with a blunt knife. In rough bra and bra wares, no le than 16,240 cwts. were manufactured in the Pru ian States in the year 1832. For musical purposes, the bra wire made in Berlin, has acquired great and merited celebrity; but that of Birmingham is now preferred even by foreigners. Bra Colour , for staining gla , is prepared by exposing for several days thin plates of bra upon tiles in the leer or annealing arch of the gla -house, till it be oxidized into a black powder, aggregated in lumps. This being pulverized and sifted, is to be again well calcined for several days more, till no particles remain in the metallic state; when it will form a fine powder of a ru et brown colour. A third calcination must now be given, with a carefully regulated heat; its quality being tested from time to time by fusion with some gla . If it makes the gla swell, and intumesce, it is properly prepared; if not, it must be still farther calcined. Such a powder communicates to gla , greens of various tints, pa ing into turquoise. When thin narrow strips of bra are stratified with sulphur in a crucible, and calcined at a red heat, they become friable, and may be reduced to powder. This being sifted and exposed upon tiles in a reverberatory furnace for ten or twelve days, becomes fit for use, and is capable of imparting a calcedony, red or yellow tinge to gla by fusion, according to the mode and proportion of using it. The gla -makers’ red colour may be prepared by exposing small plates of bra to a moderate heat in a reverberatory furnace, till they are thoroughly calcined, when the substance becomes pulverulent, and a umes a red colour. It is then ready for immediate use. Bra Colour , as employed by the colourmen to imitate bra , is of two tints, the red or bronze, and the yellow like gilt bra . Copper filings mixed with red ochre or bole, constitute the former; a powdered bra imported from Germany is used for the latter. Both must be worked up with varnish after being dried with heat, and then spread with a flat camel-hair brush evenly upon the surface of the object. The best varnish is composed of 20 ounces of spirits of wine, 2 ounces of shellac, and 2 ounces of sandarach, properly di olved. See Varnish . Only so much of the bra powder and varnish should be mixed at a time as is wanted for immediate use. Bra Foil. Dutch leaf, called Knitter or Rauschgold in Germany, is made from a very thin sheet bra , beat out under a hammer worked by water power, which gives 300 or 400 strokes per minute; from 40 to 80 leaves being laid over each other. By this treatment it acquires its characteristic solidity and lustre. See above, the proce for converting the copper superficially into bra by the fumes of zinc.