This Black Spot Destroyer is all that you need to eliminate black spots - even on outdoor spaces that haven't been treated for years! Once this extreme black spot remover has been applied and thoroughly rinsed, your outdoor space will look bright and clean - even in those previous high-traffic areas! Our Pro-Kleen Black Spot Destroyer is the perfect product to use on your outdoor surfaces to get them looking bright and clean. It can be used on block paving, natural stone, Indian sandstone and more. Pro-Kleen's Black Spot Destroyer is extremely easy to use. Black spots are known as lichen, and they appear when bacteria or algae combine with a fungus. The two organisms then anchor themselves to a surface to create stubborn black spots that are nearly impossible to remove. Black Spot Remover breaks down the source of those stubborn spots - bacteria, algae, and fungus - from hard surfaces, so you can simply rinse them away! Using a pressure sprayer, apply the solution onto the affected area and leave to soak for 2-4 hours. Then rinse thoroughly to reveal a clean and bright outdoor space! ProKleen Ultimate Black Spot Remover Destroyer Patio Cleaner 2 x 5L in Clear