Posted by Dan Schultz on December 23, 2003 at 09:55:22:
In Reply to: Red Rot on vintage instruments posted by Red Rotney on December 23, 2003 at 07:30:44:
Watch for areas on the leadpipe and valve knuckles that appear to be 'spongy-looking' or can't be polished. I've seen instances on silvered horns where the silver might still be intact but the underlying brass is gone. Pull out the pistons and look for pock marks where the nickel is still intact but the brass has deteriorated beneath. These areas can be very thin and still not be leaking. I just finished working on a little Conn euph. The tubing at the knuckles was so thin that I literally pushed through what was left of the brass attempting to remove some dents. It turned out the horn was too deteriorated to even think about patching. What happens with red rot is that the zinc in the original brass migrates out and leaves behind a porous material that is literally crumbling. My experience is 'if you see it in one spot, there is much more you can't see'.