#1 Deck Wood Cleaner is a powdered concentrate that is mixed with water. It safely cleans and restores the natural beauty of exterior wood. This product also cleans weathered composite lumber removing stains caused by mold mildew and algae along with the silver-gray color that can develop over time. Restores all wood surfaces to their original appearance. #1 Deck Wood Cleaner will not harm wood fibers pets grass or most plants. This product is step 1 of a 3 step system. #1 Deck Wood Cleaner removes dirt grime mold and mildew stains and weathered graying from horizontal and vertical wood surfaces. It is recommended for surface preparation prior to application or reapplication of wood stains. For best results use #1 Deck Wood Stains. It also works great as a whole house cleaner including vinyl siding patios sidewalks and driveways. It can be applied with a pump-up garden type sprayer or using a car wash type brush.