Question: what is the best thing to use on black mold?
Answer: Mix 1 cup of bleach and 1 gallon (3.8 L) of water.
Use a spray bottle or a bucket and sponge to apply the bleach mixture to the area with black mold.
Let the bleach sit on the mold for an hour. You can wipe it away later if that is your preference, but this isn't necessary.