Very Old Tub Stains
A little background: I'm going to be helping my Nana pack to move to my state in June. Her husband past away, and he was in charge of cleaning his bathroom. He didn't clean the bathtub that often for years, so a hard water stain and probably soap scum stain is set in on the tub.
My Nana asked me if I knew of anything to take off the stain. She's tried Tilex, a commercial cleaner recommended by the realtor, and a pumice like stone designed for cleaning tubs naturely. She's been working on the tub for a while, but has only seen some improvement. She's wanting to try a few more things before she gives up.
I've been searching the net, and will consult books in the library. I would appreciate any suggestions.