Posted by Steve Inman on February 01, 2001 at 22:11:58:
In Reply to: Re: Re: Re: Metallurgy posted by Rick Denney on January 31, 2001 at 17:49:59:
Since I don't know either, I'll be happy to also chime in!
Annealing is the process of heating metal significantly, and then cooling the metal gradually. This is the opposite of the cryogenic freezing process. Annealing is known to release internal stresses in metal. Freezing the horn first increases, then decreases the internal stresses back to where they were. But there is no permanent change in the crystal structure of the brass.
The reason annealing would/could change the sound of an instrument is that the state change of the metal means that the crystaline structure of the metal changes, and therefore other properties should also change, right? Like elasticity, density, etc.?
However, as discussed at length a few months ago on the tubaeuph forum, other processes like heating/quenching (fast cooling), and hammering are also used in the manufacture of a tuba. Each of these has different effects on the sound of the horn. I believe it was mentioned on the tubaeuph forum that annealing leaves brass "softer" than the process of heating, bending, quenching, hammering, etc. So there may be reasons brass instruments can't/aren't annealed later on in the manufacturing process. And of course, once assembled, you run the risk of melting the solder, and then disassembling the horn again!
DOH!