Maybe the scum is coming from the pitch. After leaving the tool to rest on the mirror for about 5 minutes, even after rinsing the mirror off, I can see the pattern of the lap on the mirror. Anyone know of any sources in Denver that I can get new pitch/cerium oxide? Any ATMer's in Denver besides me!?!? I am running out of CO and don't wanna wait a week or more for mail order. thanks bob-Denver,CO