[Boatanchors] Tarnish on APC Var. Caps.

[Bill Stewart]

While the discussion is on cleaning copper, let me ask about removing tarnish. 
I have a number of APC type var. caps. in the front end of a superhet I'm rebuilding. The plates are black with tarnish. Anyone know of a commercial or homebrew solution I could dip them in to remove the tarnish. I can't use a brush or do any rubbing and also I don't want to loose the settings. I also don't want to damage the porcelin/ceramic insulator material. Any suggestions will be appreciated...thanks, Bill K4JYS