Sprayed the remover on a test patch of my sandstone, waited, and watched pinprick black spots fade like old ink. That was the moment I knew the rest of the patio would come back to life. I protected the nearby plants with a quick cover and kept pets inside. After the rinse, the color looked years lighter. Delivery was easy and the instructions were genuinely clear. Strong stuff, so handle it with respect, but wow, satisfying to see the slabs clean again.