Obs. The common practice in the glass-houses is to conduct the calcination by exposing the metal, placed on tiles, in the leer or annealing arch of the furnace; a plan both convenient and economical.
BRASS′-WORK. Articles of brass and copper, when not varnished or lacquered, may be cleaned and polished with sweet oil and tripoli, rotten-stone, or powdered bath-brick, applied with friction on flannel, and ‘finished off’ with leather; due care being taken to ensure the absence of anything gritty, which would scratch and disfigure the surface of the metal. A strong solution of oxalic acid in water gives brass a fine colour. Vitriol and spirits of salts make brass and copper very bright, but the polish thus obtained soon tarnishes, and the articles consequently require more frequent cleaning. A strong lye of roche alum and water also improves the appearance of brass. In all cases where acids or saline matter has been used, the metal should be at once well rinsed in clean water, and then wiped dry, and finally dry polished with soft leather.
Brass inlaid-work may be cleaned with tripoli and linseed oil, applied by a rubber of felt or leather; the whole being afterwards thoroughly rubbed off, and then finished with clean soft leather. The ornaments of a French clock, and similar articles, are said to be best cleaned with bread-crumb, carefully rubbed, so as not to injure the wood-work. Ormolu candlesticks, LAMPS, and BRANCHES, may be cleaned with soap and water. Lacquered and GILDED ARTICLES are spoiled by frequent rubbing, and by acids and alkaline leys.
1. A fine colour may be given to BRASS ORNAMENTS, when not gilt or lacquered, with a little sal-ammoniac, in fine powder, moistened with soft water. The articles must be afterwards rubbed dry with bran and whiting. Another plan is to wash the brass-work with a strong lye of roche alum (1 oz. to water 1 pint), and after rinsing it in clean water and drying it, to finish it off with fine tripoli. These processes give to brass the brilliancy of gold. See Brass-paste.
2. A gold varnish for giving a beautiful gilding to brass and bronze objects is prepared from 16 grams of shell-lac, 4 grams of dragon’s blood, 1 gram of turmeric-root, and 332 grams of rectified spirit of wine. The varnish is thinly stroked over the surface with a sponge, the metal being warmed over a small coal fire.
The surface at first appears dull, but soon after it appears as if most beautifully gilded. The ready-prepared spirituous varnish must be preserved in well-stoppered vessels.—Dingler’s Journal.
BRASS′ING. Syn. Brass-coating. 1. Copper-plates and copper-rods may be covered with a superficial coating of brass by simply exposing them, in a heated state, to the fumes given off by melted zinc at a high temperature.
The coated plates and rods are rolled into thin sheets or drawn into wire. The spurious gold wire of Lyons is said to be made in this way.
2. Vessels of copper may be coated with brass, internally, by filling them with water strongly soured with hydrochloric acid, adding some amalgam of zinc and cream of tartar, and then boiling the whole for a short time. This plan may be usefully applied in certain cases to copper boilers in laboratories, and to other purposes.
3. By the electrotype (which see).