Prep. Brass is now generally manufactured by plunging copper, in slips, into zinc melted in the usual manner. The former metal rapidly combines with the fluid mass, and the addition is continued until an alloy somewhat difficult of fusion is formed, when the remainder of the copper is at once added. The brass thus obtained is broken into pieces, and remelted under charcoal, and a proper addition of either zinc or copper made, to bring it up to the colour and quality desired. It is next poured into moulds of granite. Before being submitted to the rolling-press for reduction to thin plates it undergoes the operation of annealing.
The proportions of the metals forming this alloy are varied according to the desired colour, and the purposes to which it is to be applied. The following formulæ are founded chiefly on analyses of standard brasses and yellow metals, made expressly for this work. Small fractions are omitted; the nearest whole numbers being generally taken:—
a. Fine Brass:—1. Copper, 2 parts; zinc,
1 part; either combined, as explained above, or the two metals separately melted, suddenly poured together, and united by vigorous stirring.
2. Copper, 7 parts; zinc, 3 parts. Bright yellow; malleable.
3. Fine copper, 4 parts; zinc, 1 part. Deeper coloured than the last; an excellent and very useful alloy.
b. Malleable Brass:—1. Copper, 33 parts; zinc, 25 parts; as before.
2. Copper, 3 parts; zinc, 2 parts. These alloys are malleable whilst hot.
c. Red Brass. This name is commonly applied to all those alloys which do not contain more than 18 to 20% of zinc. In the deeper-coloured foreign varieties (RED TOM′BAC) the per-centage of copper occasionally amounts to 88, 90, or even 92%.
d. Yellow Brass. See Fine Brass (above).