Posted by Joe S. on February 26, 2001 at 23:57:45:
In Reply to: Breaking in New Piston Valves posted by Larry Zaidan on February 26, 2001 at 18:32:10:
Sean is absolutely correct, but here is how it works:
When brass instruments are new, the interiors of the valve casings form a coating of patema/brass oxide/whatever-you-want-to-call-it.
During that time, that brass oxide LOVES to electro-plate itself over to monel (and sometimes nickel plated or stainless steel) pistons. The friction of the pistons against the casings (static electricity), plus a bit of your nasty spit mixed with water as a "plating solution" causes this (probably?).
There are TWO main reasons to use a LOT of oil:
1/ You will "insulate" the pistons from the oxidizing casings, discouraging this annoying plating over of patema to the pistons.
2/ As you scuff the patema on the casings smooth (Oxidation forms quite "jagged" and "rough".) with the pistons, oil will liquify and wash away the stuff that you scuff off the casings.
Once the casings are "good and oxidized" PLUS scuffed smooth (stabilized, so to speak), they will be "broken in".