Q: I am trying to remove a solidified layer of black rubber carpeting underpad from a hardwood floor. Can you suggest a solvent to soften it? It seems to respond to acetone-based nail polish remover, but I would need gallons.
A: If it responds to acetone, you can buy that in larger quantities at any paint store. However, be aware that the acetone will also remove any varnish or polyurethane that may be under the padding.
Have you tried scraping it off in hardened state with a drywall trowel or scraper?
If it does chip off, the way to go may be to leave it dry and work at it.