Bought this to clean a metal roof. Mixed and sprayed roof just like the instructions show. No immediate difference nor much of a difference after 2 weeks so I Sprayed roof a second time and week later still no difference.. Not only did I waste the money on this product also wasted my time spraying this product on my roof 2 different times. I had high hopes for this product after seeing absolutely no results to say i was disappointed would be an understatement. If your looking for a short cut to clean a metal roof this is not your answer..