DIYbanter - Clean dirty bathtub

On May 26, 4:08*pm, " wrote:
My bathtub has a stain in it that is impossible to remove so far. Here
is a picture of it:http://www.flickr.com/photos/5423000...7629878927850/.

What should I use to remove the stain? I tried bleach and it does not
work. It feels rather rough and even powderly at the stained area.

Thanks

Despite Evan's pronouncement that the problem has been identified and
a solution determined.....

I'd like to ask a couple questions.

What is the tub material?
Porcelain over cast iron porcelain over stamped steel?

Porcelain over stamped steel tubs do not behave as well as cast iron
ones.
Stamped steel tubs are not nearly as stiff as a cast iron tub.
Stamped steel tubs are susceptible to localized deflection & thus
damage to the porcelain coating.

When the tub is used & then drained, does some water remain in the
areas of the stain or does the tub drain completely with not a bit of
water remaining?

If small puddles of water remain in the stained areas, this situation
might be one of years of evaporative deposition.

Just adjacent to the stain (like within a few inches) is the porcelain
smooth, glossy & in good shape?
If the adjacent areas are in good shape & the tub allows water to
puddle then Norman's suggestion that lime deposits might be the
problem is worth a look.

Deposits warrant the use of an acid "cleaner" like CLR.

Let us know how things turn out.

cheers
Bob