Mildew is one of the most common effects of damp or flooded conditions.
Mildew and mold are from the same family of organisms. The mildew fungus causes staining with an irregular shape. The appearance ranges from gray to black, but sometimes is yellow to red in color. It leaves a musty odor and sometimes causes fabric degradation. Mildew is most likely to develop on cellulose or protein fibers.
Removing mildew is very difficult. The most effective method is to wetclean the garment in oxidizing bleach. Sodium hypochlorite (chlorine) bleach is the only product that actually kills and deodorizes mildew, but this bleach is not suitable for silk, wool, nylon, or spandex. Other bleaches, such as hydrogen peroxide or sodium perborate, may lighten the mildew staining sufficiently on fibers or colors where chlorine cannot be safely used. However, this will not kill the mildew, and the growth can resume. Be sure to use the appropriate bleach for the fiber type and test for colorfastness prior to any treatment.
If the dye is not colorfast to any of the oxidizing bleaches, test for colorfastness with ammonia and detergent because this may improve the garment.
Moisture, and a lack of ventilation and light accelerate mildew growth. Therefore, items in plastic bags should be processed immediately to help prevent mildew growth.