My mother-in-law has her wedding gown. She lent it to someone and when they returned it to her it has full of tar stains on the bottom of the dress. The stains have been there for years and are hard and don't want to come out. I want to use her wedding dress, but I need help with a solution to remove the tar stains. The stains are about 2 to 3 years on the dress. Please help.