Black mold spots gone in minutes, yes there is a light brown smudge left over but can be left to weather off or brush off with a stiff brush. Use the product in a small sprayer to save and extend liquid.

5/5 would recommend, sprayed it on mold under 3 minutes it was gone and hasn't came back.

I used this in my attic where we had a roof leak. I sprayed it on the underside of the roof sheathing to kill the mold/mildew that accumulated from the leak. Rmr worked very well actually. However when I ran out of rmr, I switched to household bleach and it did basically the same thing. So in my view, even though this product does produce very good results, I don't think I'll use it again. I'll try bleach first next time. It's way cheaper.