Yeah, I only have glass pieces (well, only one right now, but thats cuz I'm broke and my car is broke :P )... But I just heat up the water to a boil with the piece in there (or pieces) and let it boil till they are clean, works really well... Like I said though, you have to cook the resin dry. And this last time I have noticed a oily layer forming on the top... Dunno if its worth trying to skim or not though.