I just bought an aluminum covered steel muffin pan made by Chicago Metallic. As I was greasing the tray with melted butter, I noticed my brush was turning grey. Then I tried to clean the pan with a sponge. That turned grey. I washed the pan again (as I'd done the night before) and this grey residue continued to stick to my sponge, brush, paper towel. It was at this point I abandoned my frittata preparation to pull out a non-stick version I had bought as a backup.
What is this grey residue? I've heard non-stick pans have toxins that people avoid by buying cast iron or aluminum pans. Has anybody else had this problem?