There are many types of brass:
- Yellow Brass = 70% copper, 30% zinc
- Gold Brass = 87.5% copper, 12.5% zinc
- Red Brass = 90% copper, 10% zinc
- Nickel Silver = 65% nickel, 32% copper, 1%iron
- Bronze = copper and tin
Yes! Nickel silver is a type of brass and it actually doesn't contain any silver. Clarinet keys, some flute keys and some French Horns are made of nickel silver. These days, clarinet and flute keys are silver or nickel plated to make them last longer.
Brass is susceptible to red rot, which is the dezincification of the brass. This is when the zinc oxidizes out of the brass alloy before the copper, leaving a pink brittle area. The red/pink colour is the exposed copper. The less zinc there is in the brass, the more resistant to corrosion the brass it will be. A content of less than 15% zinc can help reduce corrosion, as does adding 1% tin. Lead pipes on trumpets are often made of gold or red brass for this reason.
The copper in brass gives it an anti-germ quality. That is why, for example, doorknobs are made out of brass, as are mineral sanitizers for swimming pools. I thought this was interesting.
Another interesting fact about brass alloy is that about 90% of it is recycled, as it can be easily separated from the magnetic metals. All those instruments that are past their use-by date can be recycled, as well as those inexpensive, unfortunate Chinese purchases. They still have some value! Ask us about this.
Brass is easy to work with and has good acoustic properties. The softness or hardness of the brass is dependent on the proportions of copper and zinc. Bells on brass instruments make use of this fact.
Red rot or corrosion can be avoided simply by cleaning your instrument thoroughly once a month and blowing oil through your horn. The oil will go some way towards protecting the bore of the instrument from the carbonic acid that results when the carbon dioxide in your breath combines with moisture. If you drink carbonated drinks while playing, you produce even more carbonic acid which attacks the zinc in the brass, exposing the copper. In addition, moisture left inside the instrument can encourage the growth of bacteria on the interior walls of the bore. Once the red rot/dezincification has exposed the copper, it creates a build up of 'copper hydroxy carbonate' that cannot be removed with soap and water. To get rid of it, you will need to have your instrument chemically cleaned on an annual basis. If it is not removed, the slides can fuse under the build up.
