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Textiles made from natural fibers are hygroscopic -- they absorb water or moisture very quickly and desorb it (dry out) very slowly. High humidity, warm temperatures, and poor ventilation encourage mold growth. Microscopic spores of fungi and bacteria are always present in the air. Generally, stagnant air above 80% relative humidity (RH) will support mold on cellulosics -- cotton or linen. Above 92% RH, on wool and silk will be affected. Soiling, organic residues, and stains from the indiscriminate handling of textiles will enhance the growth of mildew on fabrics at lower relative humidities. Humid air that is cooled but not dehumidified will have a very high relative humidity.
Remove the affected textiles from the damaging environment by supporting them with the existing (even damaged) boxes or cardboard. Spread the textiles carefully upon clean, absorbent, dry surfaces. Allow the textiles to dry. Use fans to increase the air circulation in the vicinity of the objects, do not focus fans directly upon the weakened, mildewed textiles. For single objects, a hair dryer at low temperature may be effective. Do not use an oven or microwave!
Review the previous storage or display area for structural defects (inadequate insulation, damage to pipes, flooring, ceiling). Review the rate of air circulation. Improvement in air circulation can be achieved four ways: by installing fans, by installing dehumidifiers, by installing air-conditioners (if they lower the relative humidity as well as the temperature), or by raising the temperature to lower the relative humidity. Once the mildew has dried, the residues of mildew can be removed by gentle vacuuming action with a HEPA filtered vacuum cleaner. Test the technique, the vacuum suction pressure, the effect of the brush on a small trial area of the fabric. A soft brush may be used to loosen the residue, if the fabric beneath is sufficiently strong. Washing or dry cleaning is not recommended.
The portion of the textile that is obscured by mildew is weaker than the unaffected areas. Chemical treatment ("wet-side spotting") may be deleterious to the fabric, to the dyestuff, and/or to the finish. If the growth has damaged enough fiber surface, removing the growth will reveal a perceptively damaged--and perhaps discolored area. Radical treatment may only abrade this surface more; washing and agitation may increase the likelihood of rips, tears, and holes.
Geographical, climatic factors should be considered. In some areas of the country, seasonal changes can adversely affect the conditions in the storage or display area proposed. Because of their hygroscopic nature, textiles can be damaged by spikes of high humidity. Monitor the area chosen periodically to check the temperature and humidity levels. Attics, basements, closets against exterior walls are places susceptible to changes in temperature and hence to changes in relative humidity. They are not recommended for textile storage.
However, these agents may damage some dyes, do cause discoloration of plexiglas, and are deleterious to human health. Thus, if these anti-mildew agents are used, the dry objects should be stored in sealed, closed, air tight containers like metal, waterproof trunks and well aired before use or display.
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Updated: September 2006; 2012