HarryS wrote:
We have a black stain on the bottom of a procelain bathtub. We
thought that this stain was mildew but our old tried and true
solution to mildew in the bathroom (a solution of 20% liquid laundry
bleach that will eliminate mildew stains from tile grout, tub caulk,
etc.) didn't even faze it. Scrubbing doesn't affect it. The stain
doesn't cover the entire bottom of the tub evenly, rather it's
somewhat mottled in appearance. It's a little rough to the touch.
We live in Springfield, MO and have seen a tub in another home with
this same type of stain and those folks couldn't get it off either.

Does anyone have any idea how it can be removed.

Unless the finish is worn (usually very old fixtures) it is likely the
result of the local water and maybe the water softener. Sulfur as I recall
reacts with several things to cause a black stain.

I don't know how to clean it, but IDing it is a good first step to
finding out how and how to prevent it in the future.

--
Joseph Meehan

Dia duit