Doughmakers 10051 Grand Cookie Sheet 14" x 17.5", Aluminum, Silver

Why does mine stain so easily? It has lots of brown stains on it after only a dozen or so uses.

I have a set of these Doughmakers products and I have loved them. However, after 10 years they are getting a dark gray film or powder that comes off on my hands. Has anyone had this happen? Is there a way to save my cookie sheets?

how deep is it ?

what is the gauge of the "Heavy gauge aluminum" there are numbers that are more decriptive than heavy dose anyone know the gauge number???