I think you are sputtering, too. The brown stains on the porcelain are probably metal oxides. You probably will have to clean them off, eventually. But, possilby a reversal of polarity for a little while will do some cleaning for you. As you get below 1 micron, I would expect this to diminish for you.
Dave Cooper
Created on Wednesday, June 06, 2001 3:20 AM EDT by David Cooper