Three years ago, we installed a large multi-level composite deck at our home in Cleveland. We chose composite because of the promise of no maintenance. The deck looked great for about a year, until black spots began to appear. I tried power washing, which didnt help at all, and we had to be careful not to damage the deck. I then tried scrubbing the smaller deck with bleach. I spent several hours on my hands and knees scrubbing, but the black spots remained. I was completely depressed and thought we would have to live with black spots or replace the deck. After researching the problem online, I found Corte-Clean. It took two applications at full strength and some scrubbing with a push broom, but the deck looks brand new. I have recommended the product to several friends, and I am trying to convince my local Ace Hardware to stock the product. Thank you Corte-Clean!