An Introduction to Alloys, Part 2
Brass
Hello readers, it’s time for metallurgy class again, this time focusing on brass. Brass is the second most common metal we handle at Progressive Bronze, and it’s offered as an alternative to bronze for nearly everything we make.
Where as bronze is an alloy of copper and most often tin, brass is an alloy of copper and zinc. It popped up some time after bronze, in the first millennium BC. Its composition was not well understood for more than 2000 years, as zinc in metallic form wasn’t known until the Medieval Period. The first brasses are thought to have been ‘natural’ brass, meaning the copper ore contained significant amounts of zinc, which when smelted created a low-zinc brass. By the time of the Roman Empire, however, a process called cementation was used to create brass in which copper was heated alongside the zinc ore calamine. In this process the zinc becomes vapor and permeates the copper. This process is effective, but it makes the zinc content difficult to control and also adds any impurities that are present in the calamine. This process was the dominant way brass was made until direct alloying with zinc gained popularity in the 18th century.
Brass has a lower melting point and is more malleable than bronze which makes it easy to work in to shapes from sheets or to cast. It also has antimicrobial characteristics, which makes it ideal for things like door knobs and handrails in public places. Color-wise, in comparison to copper and bronze it is very yellow, and has sometimes been used as an inexpensive substitute when an golden look is desired.
Historically brass has been heavily used as coinage, buttons, metal church appointments, ammunition cartridges, and musical instruments, among many other items. All of these things continue to be made of brass today. A number of new brass alloys have also been developed for specific purposes, but almost all still contain zinc as their secondary metal. For instance, “Nordic Gold” contains 5% zinc, 5% aluminum, & 1% tin and is used for Euro coins.
I hope this short primer has shed some light on basics this extremely common metal, so that next time you turn a brass knob, or listen to a trumpet you’ll appreciate it just a bit more. And as always, if you have any questions, or projects you’d like us to take a look at, send us an email.
