- Bond It - High Strength Brick & Patio Acid Cleaner - 16%,, Great stuff, i tested it out a small part of my garden wall, did'nt do all what i wanted to do as the weather was bad and there's no big rush.. "red brick that's gone black over the years and had moss on it, about a half meter square",, Put it on with an old sweeping brush,, give it a good brushing as the black stuff was really bad, Washed it down with the hose and she come up like new,, I should have taken a pic - before + after,, if you are buying this you just be careful this is a strong acid