How can I remove black stains on a porcelain bathtub caused by clothes
dye? I washed a pair of black jeans and hung them to try over the tub
and the drips caused stains that I've been unable to remove.

So far, I've tried bleach, ammonia, comet and ajax powder cleansers and
TSP, but none have removed or lightened the stains.

Thanks for any help.

Kelly