The money back guarantee isn’t necessary. I did it on Saturday (your video instructions on line are much better than the written ones, I just did what you did) and it came out gorgeous, almost like a new bathroom. I am really happy with this product. Two questions: How long do you leave it before showering (we already did after 24 hours and it seems ok) and how do you get this stuff off your fingernails!! I hope I have enough goop left to do my kitchen backsplash, which is also tile. Thanks.