Posted by Wade on August 25, 2003 at 23:52:22:
In Reply to: Dents posted by Question on August 25, 2003 at 22:55:49:
Brass instruments are made from tubes and sheets of brass of varying thicknesses.
A good average thickness for a slide tube (in my experiences, mind you) is about 0.5mm. My Alexander, as well as many older tubas, are made of much thinner-walled tubing and sheets. Many modern tubas come in a much heavier gauge of wall thickness.
Then you must consider the "hardness" of the brass.
Brass is an alloy of copper and zinc. (For those who think that tin comes into play, well, that would be a type of bronze.) The copper is really soft and "bendy" and lousy for tubas (unless you are into marching with a flop-o-phone) but is very workable and sounds very nice. Zinc is an electric-yellow metal that is very brittle and flaky. To combine those in a (very roughly) 75% copper/25% zinc alloy will give you a form of brass. (These percentages are misremembered by me, but are really unimportant for this discussion.)
Add more copper and you get red brass; more zinc and you get gold brass. Yellow brass is the basic starting point, here. Each of these three sub-groups have differing resistance to corrosion and bending. Each has a different sound quality.
Add nickel to the mix (in a specific amount) and you will have nickel silver, or German Silver, as some like to label it. It is very hard and resistant to Red Rot, but is is a royal pain to bend and work with. But better tubas have many of the bearings and wear points made of nickel silver as a means to prolonging the life of the instrument. Examples of this would be inner and outer slide legs, rotor casings, ferules, bow guards, keels, mouthpiece receivers, leadpipes, and bell garlands; it is not just there to look good.
Many of the so-called "easily dentable" tubas are thin, "soft" and have no nickel silver parts; they are subject to certain particular injuries from accidents or misuse/abuse/filth.
Tubas made exclusively of nickel silver (not nickel-plated brass) are likely to last forever if cared for properly, but are as rare as hen's teeth. And they have a distinctive, aggressive sound that some do not care for. (I do, however.)
So a tuba with softer brass that uses thin-walled tubing will be very prone to denting; conversely, they are also easier to repair. But most tubas do not fall into this category.
I hope that I helped you out "getting" this topic. I grossly over-simplified many details. I am sure that someone here will correct anything that I flat out got wrong.
Wade "blah, blah, blah" Rackley