ace, because if they did the Muntz metal would quickly deteriorate) (9:166). A form called "admiralty" or "naval" brass contains tin, plus Cu and Zn, which increases this alloy's corrosion resistance to sea water (6:277).
Brasses are more technically divided into three classes, based on the phases or structures of their solid portions at various forming temperatures and Zn-percentage contents (14:19). These are the "alpha brasses", comprised of up to 35% Zn; "alpha+beta brasses" having between 35 and 46.6% Zn; and the "beta brasses" containing between 46.6 and 50.6 % Zn (14:19). Others, containing even more zinc, are rarely formed or used; but there are possibilities to include gamma, delta, eta, and zeta forms--described below.
A Thousand Years of Brass-Making. Most ancient brass was made by a "cementation process" that had an upper-limit Zn content of about 28% (14:19). Zn and Cu ores were mixed together, cold, in a common crucible, and smelted together; zinc was absorbed into--dissolved within--the copper during the reduction (14:19).
The cementation process "remained the standard European method of manufacture until the beginning of the nineteenth century" (1:9). Finely divided copper metal was mixed with a zinc salt, oxide or carbonate (calamine), plus charcoal, and the mixture was placed in a closed crucible. Upon heating, the zinc ore was reduced to vaporous metallic zinc, which then diffused into the copper, forming brass (1:11).
In the process, the temperature had to be very carefully controlled [and the ancients who used the process probably did that all by color and artful 'feel,' there being no way to measure such temperatures with any accuracy]; because zinc does not vaporize below 918?C, and pure copper will melt at 1083?C (1:9). As Zn diffuses into Cu, the melting point of the alloy falls and becomes less than 1000?C when it contains as much as 30% Zn (1:9). At the end of the cementation process, heat...