brasses

Brass is an alloy of copper and zinc, harder and more workable than its component metals. The earliest such alloy, called calamine brass, which dates to Neolithic times, was probably made by reduction of mixtures of zinc ores and copper ores. More malleable than bronze, brass was used to make ewers and basins, lamps, bowls, jugs, and countless other household items. Brass production thrived under the ancient Romans— who employed it primarily in vessels, dress armor, jewelry, and brooches or clasps— then declined after Rome withdrew from northern Europe, and resumed during the Carolingian period. Europeans of the 13th to the 17th century used monumental brasses to commemorate the dead. Set into the tomb’s surface were engraved brass memorial plaques depicting the deceased, often embellished with inscriptions, heraldic devices, and other designs appropriate to the individual. Before the Spanish begin to flood Europe with silver and gold from the Americas, brass basins and plates, hammered and embossed with elaborate designs, were tremendously popular as decorative showpieces for the homes of the bourgeoisie. Once silver and gold became the high-end decorative metals of choice, brass found employment in the manufacture of utilitarian household wares and chandeliers, candlesticks, sundials, and clocks. Forged, cast, chased, and decorated with engraving, the venerable alloy also became a major material for the manufacture of fine instruments for astronomy, surveying, navigation, and other scientific pursuits. Brass has found its way into modern language as a synonym for high-ranking military officers and civilian officials (from the gold braid on the hat); as the term for a category of band or orchestral instruments made of metal; and as a word meaning bold self-assurance, or effrontery. Copper-zinc alloys are more easily worked, harder and less strong than copper-tin alloys. The malleability of brass depends on the zinc content. Brasses that contain more than 45 percent zinc are not workable, either hot or cold. Known as white brasses, these alloys are of little industrial importance, although a granulated form is used in brazing (soldering); they also form the basis for certain alloys used in die-casting. The subdivision of malleable brasses are the alpha brasses, which generally contain less than 40 percent zinc and can be worked cold, and the beta brasses, which have a greater zinc content and require hot working. The alpha brasses are widely employed in the manufacture of pins, bolts, screws, and ammunition cartridge cases. The beta brasses, less ductile but stronger, are thus suitable for the manufacture of faucet handles, sprinkler heads, window and door fittings, and other fixtures. A third group of brasses includes those alloyed with elements other than copper and zinc, added to improve physical and mechanical properties, corrosion resistance, or machinability or to modify color. These include the lead brasses, which contain 0.5% to 3.0% lead and are more easily machined; the naval and admiralty brasses, in which a small amount of tin improves resistance to corrosion by seawater; and the aluminum brasses, which provide strength and corrosion resistance where the naval brasses may fail. Cartridge brass contains 70% copper, red brass contains 85% copper, and gilding contains 95% copper. Certain brasses in popular use are sometimes referred to as bronze, as, for example, architectural bronze, an alloy of 57% copper, 40% zinc and 3% lead, and commercial bronze, an alloy of 90% copper and 10% zinc. Statuary bronze, containing less than 10 percent tin and an admixture of zinc and lead, is technically a brass.