We made a big mistake by storing our foam mattresses in a moist area without a rubber cover. Consequently, a black mildew permeated nearly the whole thickness of the mattresses, some worse than others. Our first reaction was to discard the mattresses as we thought it was a hopeless problem. Just to be sure there was no solution to the mildew problem, we went to the internet. Somehow, we found Mold Off^® which we thought should be used empirically before we threw the mattresses out. So we purchased a gallon of Mold Off^® and sprayed it on one mattress, lathered it in and let it soak. Then, we sprayed it again and used a thick cotton towel to absorb the excess fluid. We were surprised to see the black color gradually disappear. Some of the stubborn stains we sprayed a third time and rubbed the stains with towels which removed most of the discoloration. What shocked us the most were the unbelievable final results! The foam mattresses remained firm and free of mildew for months and months to this day! We cannot thank the producers of Mold Off^® enough for the great outcome.