I have what I think is black mold on my concrete basement floor. It has a black lacy look to it, with black blotches about =BD inch in diameter. First I used Tilex with mildew cleaner first, and it slightly lightened the look. Then I used straight Tea Tree Oil, but I only did a slight spot, since I can only buy it in small quantities and it is expensive. There was no noticeable change in the appearance of the mold. Finally, I used straight white vinegar, and it worked wonderfully. I am giving it about 95% effectiveness rate. You cannot even see where the mold was, and the change it appearance was almost instantaneously. However, you should smell my house right now. I am glad I did not pay for a high priced mold killer.=20
Mary