I found out about this product when we moved into a brand new house in AZ. Everything looked new except for the grout which had spots everywhere from construction debris. The person that came in to fix our grout used this product from This Old Grout. The transformation was not only impressive, but the cleaning thereafter was a breeze. We've moved into our 3rd brand new home and yes the grout looks horrible. So thankful there's a product available that's so easy to use, actually lasts and looks great. One last note, several yrs ago, my 4 y/o daughter decided to change our grout in the dining area by using a black permanent marker. I tried removing it with a bunch of different products, but finally decided to use the grout seal which covered the marks beautifully.