Hi Susie
There is no easy sure fire way to remove the soap stains. Depending how deep the stain is set will determine how many applications of a poultice will need to be applied.
You could do a TEST with Acetone and white non print paper towels.
Acetone is
extremely flammable! Please use caution and keep away from all open flames and sparks.
Cover the stain completely (overlapping at least 1" in all directions) with at least the equivalence of 1/2" of the paper towel and saturate with the Acetone. Cover with a piece self stick plastic wrap. Allow to sit over night. In the morning remove the plastic. Allow the paper towel to thoroughly dry out before removing.
After removing the paper towel, assess the stain. It's possible that the darkened area is larger. If that's the case, allow it to dry out.
Has the stain remained the same, diminished, or disappeared altogether? If it has diminished you can repeat the process. This may take several applications. Allow the stone to dry thoroughly between applications.
