Okay...I just bought a home that someone trashed when they calked the tub. It is a steel or metal tub. The calking is so hard and stuck on the tub and backsplash area that I soaked the calking a bit with acetone. Chiped away at it, but the fat finger that smeared it left the residue on the tub. Is is okay to soak a metal tub with acetone? Will it hurt anything? Is there anything else that might loosen this white cement type stuff? Thanks!