Grout Renewal is a safer alternative cleaner than harsh acids like phosphoric and muratic. It easily removes the embedded soil layer and renews the surface of the grout. This product is made with a proprietary organic acid that is twice as effective in dissolving calcium car_bonate than phosphoric acid but is safer for the skin.DIRECTIONS FOR USEAlways test each surface to be cleaned in an in_conspicuous area to determine compatibility with the product. Do not use on calcium based natural stone. This product will damage marble, limestone, and other acid sensitive materials.Mask off or cover all surfaces especially metal which may come in contact with overspray. DILUTION 1. Dilute product 1 to 1 with hot water into a pump up sprayer. 2. Spray evenly over the surface to be cleaned. In badly stained areas, agitate with a stiff brush to as_sist in the cleaning process.3. Remove the product from the floor using a wet dry vacuum or an appropriate tile and grout clean_ing pressure system.4. Once the floor is rinse, the pH of the floor needs to be neutralized using an Alkaline Grout Cleaner diluted at 4 ounces per gallon. Failure to neutralize the floor can result in degradation of the grout lines due to the acid nature of this product.