Posted by Joe S. on February 03, 2001 at 22:42:41:
In Reply to: Piston valve problems posted by Bill Jagnow on February 03, 2001 at 20:39:37:
I think I might know. Your valve casings were "clean" (untarnished) yellow brass when you first bought the instrument (new - right?). Now, the casings are in the process of tarnishing, of course. Tarnish, or oxidation, doesn't form on a surface like a smooth coat of paint. Rather, it forms in rough little microscopic "spikes". "Breaking in" valves means that as this rough oxidation forms on the bearing surface, YOUR job is to scuff that surface down )(through use) to a smooth, stable, oxidized surface.
If you have light yellowish, brownish, or greenish deposits on your pistons, THAT is oxidation that has electro-plated over on to your pistons. Oxidation LOVES to electro-plate over to the pistons as it is first forming on casing surfaces:
1/ The up and down piston action creates static electricity.
2/ YOU add a little "spit-water" (not great, but "OK" as an electro-plating solution).
and there you have it - brass oxide PLATED over to monel (or whatever) piston surfaces.
You can "smooth" the casings by using very gentle lapping methods - or by getting a repairman to do so - while your casings are still changing over from untarnished yellow to being coated with brass oxide. I have been chided for this on this bbs by a well-known mouthpiece-maker/machinist, but I have found the ideal solution (rather than repair or machinist supply powders, solutions, etc.) to be Lava soap suds. I lather up Lava soap in my hand, put the suds on the piston, remove the felts and corks from the piston (so as not to spoil them) and work the piston up and down for a minute or so. The big PROBLEM that YOU will have with this is that you probably don't have access to the funky brushes that I have, nor to high pressure HOT water (to remove all of the pumice-containing Lava soap. Lava contains, in my opinion, just the "right" extra-extra fine grit of pumice and the soap suds - to me - are the ideal "carrier" and "lubricant" with which to apply the pumice (which, of course, is already IN the Lava soap !) Again, an excellent repairman can gentle lap your pistons to eliminate the sticking. Try to NOT get an "acid bath" as this will remove ALL of the oxidation, and you will have to start your "break in" all over again.