My father is attempting to remove the mirror from a piece of glass. We stripped the black paint from the back and exposed the shiny surface with acetone. In the past he has been able to remove aluminum mirror with lye, but that didn't react. We also attempted bleach in case it was actually silver but that didn't react either. Is there another metal that could be used to back a mirror? Are we doing anything wrong? Also adding hydrogen peroxide to the lye made the mirror bubble but no black silver oxide or white aluminum oxide.