A customer once came to me and said he spilled a cup of coffee on his limestone hearthstone. I told him I’m not promising anything but I’ll try to get the stain out. He went to work and I fought with this stain all morning. Finally stood back and looked at it. Went to his kitchen made a pot of coffee and stained the whole thing. He came home and was flabbergasted couldn’t believe it. Payed me all is good never told him what I did.