RockSolid Deck & Patio Cleaner Concentrate quickly and safely restores dirty, weathered, and mildew stained wood to a bright natural look. Removes dirt, mildew, algae, and more. Eliminates mill glaze. For use on: wood decks, siding, fences, composite decks, and porous concrete surfaces. Fast acting. Covers up to 2500 Sq. Ft. per gallon.