Why do muffin tins get the brown/gray layers on them? I wash them each time and no muffin mix gets on them.?

Answer 1

That is grease from the oils or butters in your muffin or from you cooking spray. Use ammonia or a degreaser to remove this. It builds up and gets harder and harder to remove.

Answer 2

Its the grease/oil/butter/shortening in the muffin mix, it evaporates slightly with the water as they bake, therefore adhering to the sides of the muffin tin and frustrating dish washers everywhere! Using muffin or cupcake liners helps a little.