Pour 1 gallon warm water into a cleaning bucket, along with 2 tsp. of a laundry detergent containing borate. Read the product ingredient label to make sure borate is a listed ingredient.
Put on a pair of gloves as well as a mask if needed to prevent you from inhaling any mold vapors.
Dip a scrub brush in the solution and scrub over the moldy area. Allow the area to air-dry completely.
Pour 1/4 cup liquid bleach into the cleaning bucket.
Dip a rag in the solution and wipe over the molded area once more. Allow to air dry fully.
Saturate a rag with the pure borate-based laundry detergent, then wipe over the area where the mold had developed. This will prevent the future growth of mold in the area.