I don't know how old your steam iron is or wht the bottom is made from -- but I
had an older steam iron with metal bottom..looked like chrome but can't be
sure. Anyway, I cleaned inside with white vinegar and got out the gunk caused
by lime buildup...and it left a black stain on bottom of iron. Silver polish
removed most of it. Finally switched to newer iron and gave away the old one.
Beginning to think it was a mistake. New, lighter weight one doesn't do as
good a job.