Thanks to Kevin Gillan from www.advleather.com for this post on dealing with mold or mildew.
Source of Mold and Mildew
Spores of fungi and bacteria are present in the air. High humidity, warm temperatures, and poor ventilation provide the ambient conditions that allow mold growth. Generally, stagnant air above 80% relative humidity may support mold. If above 95%, the humidity will certainly encourage fungi and bacteria to grow. Soiling, organic residues and stains will enhance the growth of mildew on leather and fabrics.
Removing Mildew from Leather and Fabric Surfaces
First, remove loose mold from outer coverings of upholstered articles with a soft bristle brush. Do this outdoors, if possible, to prevent scattering mildew spores in the house. Wash brush before re-using.
Run a vacuum cleaner attachment over the surface of the leather and fabric panels to draw out more of the mold. Remember that the mold spores are being drawn into the bag of the vacuum cleaner. If the vacuum has a disposable bag, remove and dispose of it immediately. If not, empty the bag carefully (preferably outdoors) to avoid scattering mold spores in the house.
Do everything conveniently possible to dry the leather – use an electric heater and a fan to carry away moist air. Sun and air the article to help stop mold growth.
If you have finished leather (leather with a topically applied pigment coating), and mildew remains, sponge lightly with thick suds of soap and wipe with a clean damp cloth. In doing this, avoid getting the leather wet with excessive amounts of moisture. DO NOT USE THIS STRATEGY UNLESS YOU ARE SURE THE LEATHER HAS A FINISH ON IT (see our leather care page to help you identify your leather type). In all cases, do a test in a non-obvious area of your leather to ensure that the suds will not darken, stain or discolor the leather. If you have cushions with zipper access, and you suspect the fungi or bacteria have migrated into the internals of the cushion, remove the cushion cores and treat accordingly, or replace with new.
If necessary, a final step to remove mildew on upholstered leather furniture is to gently wipe it with a cloth moistened with diluted alcohol (1 cup denatured or isopropyl alcohol to 4 cup water). Dry the article thoroughly. Once again, apply this strategy only if you are sure it’s finished leather, and only after you have tested in a non-obvious location on your furniture. Be aware that this alcohol solution may adversely effect the top-coat and surface finish of your leather so only do this as a last ditch effort and only after thoroughly testing on a hidden part of your leather.
If mold has grown into the inner part of your furniture frame, open the underside dust cover, then dry and air out the internals as best as possible. You may need to send it to a reliable disinfecting and fumigating service. Such services are often listed under "Exterminating and Fumigating" or "Pest Control" services in the yellow pages of the telephone directory. If they have an “ozone chamber,” have them put your furniture into the chamber for at least 48 hours.
Here are some tips on preventing mildew.
- Keep The Leather Clean – Soiling can supply enough food for mildew to start growing when moisture and temperature are right. Greasy films, such as those that form on kitchen walls, also contain many nutrients for mildew-causing molds.
- Get Rid of Dampness – Dampness is often caused by condensation of moisture from humid air onto cooler surfaces. Excessive moisture may indicate that repairs or additional insulation are needed. Replace cracked or defective mortar. Some basements are continually wet from water leaking through crevices in the wall. Make sure outside drainage is adequate.
- Control Moisture – For waterproofing concrete and other masonry walls above ground, apply two coats of cement paint, tinted with mineral coloring if desired. Waterproofed coatings to seal absorbent brick and other outside surfaces may be needed. Spread a layer of moisture-barrier material over the soil in crawl spaces under houses. You can use heavy roofing paper or polyethylene plastic film. Good ventilation is important. If possible, do not enclose the crawl space. In extreme cases, a fan or blower may be needed to move the humid air from under the building. Cooking, laundering, and bathing may add 2 gallons or more of water a day to the house. If circulation is not adequate use some type of exhaust fan. If your clothes dryer is equipped with a vent, have it exhausted to the outside to remove moist air.
- Dry the Air – Cool air holds less moisture than warm air. Properly installed air-conditioning systems remove moisture from the air by taking up warm air, cooling it (which removes the moisture) and circulating the cool dry air back into the room. In rooms that are not air-conditioned-especially the basement–mechanical dehumidifiers are useful. A humidistat can be attached to the unit to control the humidity. Mechanical dehumidifiers, however, can add heat to a room. If you are using air-conditioners or dehumidifiers, keep windows and doors closed.
- Heat – Get rid of dampness by heating the house for a short time. Then open doors and windows to let out the moisture-laden air. An exhaust fan may be used to force it out.
- Circulate the Air – When the air outside is drier than that inside, ventilation allows the dry air to enter, take up excess moisture, and then be carried outside. When natural breezes are not sufficient, you can use electric fans placed in a window, set in a wall, or ducted to the attic to move air from the house. Poorly ventilated rooms get damp and musty during continued wet weather, and furniture in such a room is prone to mildew. Try to improve the air circulation. If necessary, lay the furniture on its back, cut open, or remove the dust cover under your furniture and run a fan into the open space to help dry the internals of your furniture. It may help to dry the inside by running a de-humidifier, pointing the air-flow into the internals of your furniture.
- Get Rid of Musty Odors – Get rid of musty odors as soon as possible to prevent further mold growth. Usually musty odors disappear if the area is well heated and dried. If the odors remain, the following treatment may be necessary. On cement floors and on tiled walls and floors, get rid of mustiness by scrubbing with a diluted solution of sodium hypochlorite or other chlorine bleach available in most grocery stores. Use one-half to 1 cup of liquid household bleach to a gallon of water. Rinse with clear water and wipe as dry as possible. Keep windows open until walls and floors are thoroughly dry. DO NOT APPLY THIS SOLUTION TO THE LEATHER.