The pictures on the web site were impressive but I found them hard to believe. We live in the Northwest where it rains at least half of the year, and our deck is almost completely shaded by large trees, so moss and mold are a given. For two years I tried so many things to clean the moss and mold off of our deck, and none of them worked very well. I was always left with black spots. We don't know for how many years the deck was neglected before we bought our home, but as you can see from the photo, by spring it is really a mess. I bought Corte Clean out of sheer desperation and as a last resort before just replacing the deck. I added 4 scoops of Corte Clean to a gallon of water (nearly maximum strength), sprayed it on, and scrubbed the deck with a deck brush. After 20 minutes, I thoroughly rinsed it. When it dried, we were shocked to see how clean it got. It was a miracle! It was like getting a new deck. I never would have believed it if I hadn't done it myself. I can't recommend Corte Clean highly enough!