My wife found your product on-line, She said it cleans those ugly black spots we have on our deck, I was skeptical and some of your reviews were not favorable and the price was high, I must say I was amazed how well it worked if the directions were followed exactly, especially the sunlight requirement, there is one area of my deck that was in shade, black spots in that area were not removed. I waited until later in the day when the area was sunlit and dry the second cleaning removed the spots. The best recommendation I can give is my second purchase. Thank You Paul K