Subject: How can I tell the difference between stainless steel and aluminum?

This is for a home project that relates to what I've been studying in school. It
involves a metal strainer, I'm trying to figure out if it is stainless steel
since if it is any other metal, it may pose some serious problems for straining
kefir or other things. This strainer is all mesh, and the only solid parts are
made of plastic unfortunately, so that has complicated a few ways of testing it
to see if it is stainless steel or aluminum(like trying to scratch or dent it
with a brass key). It's not magnetic, and many if not most forms of stainless
steel are non-magnetic, while virtually all aluminum is non-magnetic. It doesn't
become duller after washing thoroughly, as would many forms of aluminum. I would
appreciate as many ways of testing the metal as possible, and I would love to
understand the science behind it to help me in my schooling and teaching others.

Re: How can I tell the difference between stainless steel and aluminum?