Stonecare4U Black Spot Remover is a high-performance cleaner. It is specially formulated to remove stubborn black spots from natural stone and other outdoor stone and masonry surfaces. For best results, apply, then agitate, then leave for around 2-3 hours before rinsing off. It will quickly remove layers of dirt and grime as well as green algae, lichen and long-standing black spot deposits. Alkaline-based cleaners will not damage or etch the surface of the stone. Apply neat on areas of heavy surface contamination, or dilute 1:1 for less dirty areas. Up to 50m² per 5L when diluted 1:1. Coverage varies depending on surface contamination.