THE BRASSFOUNDER.
Casting.
Next to iron, perhaps brass is the metal chiefly employed in the manufacture of articles of daily use, and the trade of the Brassfounder is therefore of very great importance, especially in connexion with the small metal fittings, such as catches, locks, bolts, hooks, screws, and other objects used in completing and furnishing the house.
Brass is not a pure metal, but is what is called an alloy, that is, a mixture of various metals. It is composed of copper and zinc in such proportions as may be necessary to obtain various degrees of hardness and colour, according to the use for which the compound is to be employed. The best proportions for common brass are about two parts of copper to one part of zinc. Formerly brass was made by heating copper with calamine (which is the ore of zinc) and charcoal, but it is now formed from melting the two metals together. It is then cast into plates, which are either broken up for recasting into any required form, or rolled into sheets. Common brass is very malleable, is more easily melted than copper, and may be cast into any form. It will take a very high polish, does not rust or tarnish by exposure to the air, and, although it is durable in wear, is sufficiently soft to yield readily to the file and other tools used by the workmen. These properties make it useful for a great variety of purposes where steel or iron could not be so well employed.
Crucible. Magnet.
The smelting or mixing houses where the brass is made are fitted with air furnaces, and in some of the best workshops the crucibles or melting pots are made of plumbago or pure blacklead, which, although it is more expensive, is much more durable than the Stourbridge clay, of which the commoner crucibles are formed.
A very fine quality of brass for best castings consists of three parts of best selected copper, and two of spelter, with some best scrap brass and a little tin; while a second quality is formed of two parts of ordinary copper and one part of spelter, melted into ingots with a proportion of scrap brass and brass filings. Before the latter are used the iron filings are separated from them by a magnet, or by a series of magnets fastened to a revolving chain frame.