Preventing Mildew
How to Prevent and Remove Mildew — Home Methods
(Reprinted with
permission)
Wanda Eubank -
Department of Environmental Design, University of Missouri-Columbia
Betty Feather -
Department of Textile and Apparel Management, University of Missouri-Columbia
Mildew can be found on many different surfaces.
It is a thin, black, or sometimes white, growth produced by mold. Molds are
simple plants belonging to the group known as fungi. Though molds are always
present in the air, those that cause mildew need moisture and certain temperatures
to grow. They commonly develop in humid summer weather, especially in closed
houses.
These molds grow on anything from which they
can get enough food. In homes they develop most often on cotton, linen, rayon,
silk, wool, leather, wood and paper. Many synthetic fibers resist mildew.
Molds that cause mildew flourish wherever it
is damp, warm, poorly lighted and/or where air is not circulated — in
cellars, crawl spaces of houses without basements and clothing closets. It can
also be found on draperies and rugs in basement recreation rooms, on shower
curtains and on damp clothes rolled up for ironing. These molds are also likely
to grow in a new house because of moisture in the building materials.
As the molds grow, they cause considerable damage.
They leave a musty odor; they discolor fabrics; and sometimes they eat into
them until the fabrics rot and fall to pieces. They also discolor leather and
paper.
Preventing Mildew
Keep Things Clean
Keep closets, dresser drawers, basements — any place where mildew is likely
to grow — as clean as possible. Soil on dirty articles can supply enough
food for mildew to start growing when moisture and temperatureS are right. Greasy
films, such as those that form on kitchen walls, also contain many nutrients
for mildew-causing molds.
Clean clothing is less likely to mildew than soiled clothing. Because most synthetic fibers, such as acetate, acrylic, polyester and nylon,
are resistant to mildew, clean fabrics of these fibers will not support mold
growth. But even on these fabrics, soil may supply food to start mildew. Clean
all soiled fabrics thoroughly, regardless of fiber type to help prevent them
from mildewing.
Get Rid of Dampness
Control the Cause
Mold spores are present in the air and may settle onto surfaces if there is
sufficient moisture.
A damp basement, or any other structure, is often
caused by moisture condensation 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.
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.
If your clothes dryer is equipped with a vent,
have it exhausted to the outside to remove moist air.
Dry the Air
Air Conditioners and Dehumidifiers
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.
- When 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.
- Air in closets and other small areas can be dried by using an electric light
continuously (60- to 100-watt bulb). The heat will prevent mildew if the space
is not too large.
Caution: Be
sure to place the light bulb far enough from clothing and other flammables to
avoid the danger of fire.
Chemicals that absorb moisture — silica
gel, activated alumina, anhydrous calcium sulfate and molecular sieves may be
used to absorb moisture from the air. These chemicals are not likely to be found
in department stores, drug stores or hardware stores. In metropolitan areas,
look in the yellow pages of the telephone book for scientific supply houses
and suppliers of industrial chemicals. In rural areas or small towns, contact
your local University Extension center, high school chemistry teacher or the
chemistry department of a college or university. Some of these chemicals are
sold under various trade names by several companies, and others are produced
by only one company.
These chemicals are not harmful to fabrics and
feel dry even when they saturate the cloth. Hang cloth bags of the chemical
in clothing closets. Or place an open container of it in the closet —
on a shelf, preferably, or on the floor. See that the door is well-sealed and
kept closed so that moisture from outside air will not get in. You may scatter
the dry granules through layers of clothing and other articles that are to be
stored in tightly closed chests or trunks.
All of these chemicals can be used over and over
if you dry them between uses. Simply place the granules in a vented oven at
300 to 350 degrees F (149 to 177 degrees C) for several hours. Then put the
hot granules in an airtight container to cool. Silica gel and anhydrous calcium
sulfate (specially treated with a color indicator) are pink when full of moisture,
blue when dry.
Another chemical that absorbs moisture from the
air is anhydrous calcium chloride. Calcium chloride is used in some states for
melting snow on the highways, so your local road department may be able to furnish
names of suppliers. The chemical is available in small, white granules that
hold twice their weight of water. But it liquefies as it absorbs moisture. So
do not let this chemical touch clothing or household textiles; it can make holes
in them.
To use anhydrous calcium chloride, place the
granules in a simple, cup-shaped container made from nonrusting screen or waxed
cardboard (milk carton) perforated with small holes. Support the container in
an enameled pot so the liquid can drip away from the container, leaving the
calcium chloride to take up more moisture. Then place the pot in the closet,
preferably on the shelf, and keep the door shut and sealed. One pound (454 grams)
of calcium chloride will last from 2 weeks to 2 months, depending on the humidity.
When only liquid is left, discard the liquid and start over.
Caution: Add
water to the liquid before disposing of it.
Circulate the Air
Air movement is excellent at removing moisture.
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 vented to the attic to move air from the house.
Poorly ventilated closets get damp and musty
during continued wet weather and articles stored in them are apt to mildew.
Try to improve the air circulation by opening the closet doors or by installing
a fan. In addition, hang the clothes loosely so that air can circulate around
them. Dry all wet clothing (including clothes wet from rain or perspiration)
before putting it in the closet.
Cooking, laundering, and bathing may add 2 gallons
(7.6 liters) or more of water a day to the house, unless circulation is adequate.
It is often necessary to use some type of exhaust fan.
Get Rid of Musty Odors
Musty odors, which indicate mold growth, are
sometimes noticeable in basements and shower stalls. Take special precautions
to get rid of musty odors as soon as possible to prevent further objectionable
and damaging mold growth. Usually musty odors disappear if the area is well
heated and dried. If the odors remain, the following treatments may be necessary.
In basements, use chlorinated lime (commonly
called chloride of lime or bleaching powder) to remove musty odors. Sprinkle
this chemical over the floor and let it stay until all mustiness disappears.
Then sweep it up.
On cement floors and on tiled walls and floors in bathrooms,
get rid of mustiness by scrubbing with a dilute solution of sodium hypochlorite
or other chlorine bleach available in grocery stores. Use 1/2 to 1 cup of liquid
household bleach to a gallon (3.8 liters) of water. Rinse with clear water and
wipe as dry as possible. Keep windows open until walls and floors are thoroughly
dry.
Caution: Work
quickly and carefully on plastic and asphalt tile to avoid spotting the surface.
Quaternary ammonium compounds (available in janitorial,
dairy and poultry supply houses) may also be used on floors and walls. Select
a product that is registered and labeled for the particular use you have in
mind. Not all compounds are equally effective.
Aerosol sprays for cleaning and sanitizing bathroom
walls are also available.
Give Special Care to Some Articles and
Surfaces
Clothing and household fabrics
Keep fabrics dry. Never let clothing or other fabric articles lie around damp
or wet. Dry soiled clothes before putting them into the hamper. Wash out dishcloths
and hang them to dry. Spread out washcloths and damp towels. Stretch out wet
shower curtains. It is the wet curtain left bunched together or sticking to
the wall or tub that is most likely to mildew. Sprinkle only as many articles
as can be ironed in a day. Shake out and dry those not ironed.
Dry washed garments and fabrics thoroughly and
quickly. Fabrics dried slowly may get sour and musty smelling — a sign
of mold growth.
To help keep moisture out of clothing and household
fabrics and thus make them less susceptible to mold growth, treat them with
water-repellent sprays. Spray draperies, slipcovers, mattresses, overshoes and
jackets and other outer garments.
Fungicide products
that may be sprayed on fabrics to give them mildew protection are available
in low-pressure aerosol containers. Some germicidal, mothproof and water-repellent
sprays may also protect against mildew. Read labels on the container for information.
For adequate mildew protection, wet the surface
of the fabric thoroughly with the spray. Unless the sprayed fabrics are kept
in a closed container, they should be examined frequently and resprayed. For
precautions, see the section "Use of Pesticides," including fungicides.
Clean Before Storing
If clothing or household
textiles are not treated with a mildew-resistant finish, be sure to wash or
dry clean them before storing, as soiled articles are more likely to mildew
than clean ones. Unless you know that your laundry starch contains a mildew
inhibitor, do not leave starch in fabrics you are going to store; molds feed
on starch.
From time to time on warm, dry days, sun and
air the articles stored in closets. It pays to occasionally inspect cotton,
rayon, leather, and woolen clothing stored in garment bags. Unless such materials
are stored with a mildew inhibitor, they may mildew. A closed bag, dampness
and hot summer weather make ideal growing conditions for molds.
Store With a Mildew Inhibitor
Certain chemicals
give off vapors that inhibit mold growth and can protect fabrics during storage.
One such chemical, paradichlorobenzene, effectively
controls mildew on clothing and other apparel when used in packages, trunks
or garment bags kept as nearly airtight as possible. This chemical, which is
widely recommended for moth control, is available in grocery, drug and department
stores under various trade names.
Scatter paradichlorobenzene crystals through
the folds of garments to be packed in boxes, or hang bags of crystals at the
top of garment bags so the heavy vapors settle on the materials being protected.
Use about 1 pound (454 g) of the crystals for 100 cubic feet (2.8 cubic meters)
of airspace, proportionately less for small spaces. A closet 3 feet deep by
4 feet wide by 8 feet high (0.9 by 1.2 by 2.4 meters) has an airspace of 96
cubic feet (2.7 m3). As the vapors leak out, mildew protection disappears and
the chemical must be replenished.
Paradichlorobenzene is also available in spray
cans.
Caution: Do
not inhale the spray. Paradichlorobenzene damages some plastics. Therefore,
remove plastic buttons and ornaments from garments and use wooden or metal hangers
instead of plastic clothes hangers.
Paraformaldehyde is another chemical that has
mildew-inhibiting properties. It is sold in powder form at drugstores. Use paraformaldehyde
to protect stored clothing and bedding. Place bags of the chemical where the
vapors can circulate and reach all surfaces of the stored articles. Use a mixture
of 3.15 ounces (89.30 g) of actual paraformaldehyde and 0.35 ounce (9.92 g)
of paradichlorobenzene (9-to-1 ratio) for every 500 cubic feet (14.16 m3) of
airspace. A 9- by 10-foot room, 8 feet high (2.7 by 3 by 2.4 m), contains 720
cubic feet (20.3 m3) of airspace.
Low-pressure sprays containing mildew-inhibiting
chemicals will also help control molds and mildew growth in a closed area. To
be effective, the spray must wet the interior surfaces of the closet or storage
container. Thoroughly spray into cracks and crevices. Respray as frequently
as necessary.
Caution: Do
not inhale the mist from the spray, since the chemical is poisonous. And do
not use the spray near a flame.
Leather Goods (Prevention)
To protect leather against mildew, treat with
low-pressure aerosol sprays that carry specific directions. Shoe and luggage
stores may have these aerosol sprays that have been specially made for leather
goods.
Before treating the article, test the spray on
a small area where it will not show. Do this to see whether it will change the
color of the leather. Repeat the treatment as directed on the label.
Caution: Do
not inhale the mist from the spray and do not use spray near flame. Follow all
precautions given on the can.
Another way to protect leather goods
is to apply a good wax dressing. A thin coat of floor wax applied to
shoes — to both the uppers and the soles — keeps moisture out and
helps prevent mildew. Some commercially available waxes or silicon resins have
antimildew properties. However, some shoe dressings contain antifungicidal ingredients
that might discolor white or light-colored leather.
During warm, humid weather, protect stored shoes,
jackets, luggage and other leather articles with paradichlorobenzene or paraformaldehyde. Wrap the articles
along with the chemical in packages and seal them. If there is any plastic on
these articles, do not use paradichlorobenzene. Leather goods can also be protected
by wiping them with a solution of 3/8 ounce (11 g) of salicylanilide in 1 quart
(0.95 liters) of rubbing alcohol. Dry the articles before putting them away.
Wood
Unpainted Wood
In damp, warm, poorly ventilated
areas, surface mold often develops on wooden parts of buildings. Since new,
unseasoned lumber is particularly susceptible to mildew, avoid using it whenever
possible.
Painted Wood
Indoor wood surfaces covered with enamel or oil-resin paint rarely mildew. Softer paints
on outdoor surfaces mildew more readily. Molds feed on the oil and minerals
in the paint and cause a dirty-looking discoloration. They may penetrate the
paint film deeply, even to the underlying wood.
Mildew-resistant paints in all colors for outdoor
wood surfaces are available at paint and hardware stores. Manufacturers have
suitably formulated their products with fungicides to help combat mildew attack.
Caution: Mildew-resistant
paints should not be used on window sills, playpens, beds or toys because these
paints can harm small children if ingested.
Paper and Books
In damp summer weather, keep papers and books
as dry as possible to help control mold growth. If you have an enclosed bookcase,
keep a small electric light lit continuously in the bookcase or use a chemical
dehumidifier, keeping the doors closed as tightly as possible. Hang a bag of
paradichlorobenzene or paraformaldehyde in the closed bookcase. Or dust books
and papers with paraformaldehyde, then package them and seal.
Caution: Paraformaldehyde
is poisonous and may be very irritating to some persons. Avoid inhaling the
fumes.
Books can also be protected by wiping them with
a cloth wet with a solution of 3/8 ounce (11 g) of salicylanilide in 1 quart
(0.95 liters) of rubbing alcohol. Or use low-pressure sprays containing a fungicide
to protect paper products against mildew. Unless they are kept in closed containers,
respray them frequently.
How to Remove Mildew From Clothing
and Household
Fabrics
Remove mildew spots as soon as you discover them. Do
not give the mold growth a chance to weaken or rot the material. Brush off any
surface growth outdoors to prevent scattering the mildew spores in the house.
Sun and air fabrics thoroughly. If any mildew spots remain, treat washable articles
as described below. Dry clean nonwashable articles.
Wash mildew-stained articles at once with soap or detergent
and water. Rinse well and dry in the sun. If any stain remains, use
lemon juice and salt or another bleach. If you use a bleach, be sure to test
colored fabrics for colorfastness.
Lemon Juice and Salt
Moisten stain with a mixture
of lemon juice and salt. Spread in the sun to bleach. Rinse thoroughly.
Peroxygen Bleach
Mix 1 to 2 tablespoons of sodium
perborate or a powdered bleach containing sodium perborate or potassium monopersulfate
with 1 pint (0.47 liters) of water. Use hot water if it is safe for the fabric;
otherwise, use lukewarm water. Sponge the stain or soak the stained area in
the solution, or sprinkle the dry powder directly on the dampened stain. Let
solution or powder remain on the stain 30 minutes or longer, then rinse thoroughly.
If mildew stains have been on the fabric for some time,
it may be necessary to soak the fabric in the bleach solution overnight. Applying
sodium perborate solution at or near the boiling point may remove stubborn stains.
Be sure this treatment is safe for the fabric.
Chlorine Bleach
Mix 2 tablespoons of liquid
chlorine bleach with 1 quart (0.95 liters) of warm water. Sponge the stain or
soak the stained area in the solution. Allow the bleach to remain on the fabric
from 5 to 15 minutes, then rinse. An additional soaking in weak vinegar (2 tablespoons
to a cup of water) will stop further bleach action. Never use a chlorine bleach
on silk, wool or Spandex fabrics. Some fabrics with wash-and-wear or other special
finishes may be damaged by chlorine bleaches. Articles with such finishes usually
have a warning on the label or on a hang tag attached to the garment when it
is sold.
Upholstered Articles, Mattresses and Rugs
First, remove loose mold from outer coverings
of upholstered articles, mattresses, rugs and carpets by brushing with a broom.
Do this outdoors to prevent scattering mildew spores in the house.
Run a vacuum cleaner attachment over the surface
of the article to draw out more of the mold. Remember that the mold spores are
being drawn into the bag of the vacuum cleaner. If the appliance 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 article
— use an electric heater and a fan to carry away moist air. Sun and air
the article to stop the mold growth.
If mildew remains on upholstered articles or mattresses,
sponge lightly with thick suds of soap or detergent and wipe with a clean, damp
cloth. In doing this, get as little water on the fabric as possible so the filling
does not get wet.
Another way to remove mildew on upholstered furniture
is to wipe it with a cloth moistened with diluted alcohol (1 cup denatured or
rubbing alcohol to 1 cup water). Dry the article thoroughly.
Sponge mildewed rugs and carpets with thick suds
or a rug shampoo. Then remove the suds by wiping with a cloth dampened with
clear water. Dry in the sun if possible.
Use a low-pressure spray containing a fungicide
to get rid of mildew. Respray frequently, especially in localities where mildew
is a major problem.
Vapors of paradichlorobenzene or paraformaldehyde,
used in enclosed areas, will stop mold growth.
If molds have grown into the inner part of an article,
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.
Leather goods
To remove mildew from leather goods, wipe with
a cloth moistened with diluted alcohol (1 cup denatured or rubbing alcohol to
1 cup water). Dry in a current of air. If mildew remains, wash with thick suds
made from a mild soap or detergent, saddle soap, or a soap containing a germicide
or fungicide. Then wipe with a damp cloth and dry in an airy place. Polish leather
shoes and luggage with a good wax dressing.
Shoes contaminated with fungus growth on the
inside often develop unpleasant odors, and colored mildew shows up on the inner
sole and linings and up into the toe. You can remove this kind of mildew with
low-pressure sprays especially intended for freshening shoes; these sprays are
available at shoe and department stores. Use these products as directed.
Another way to stop mold growth in
leather goods is to place the leather goods in a container along
with crystals of commercially prepared paradichlorobenzene-paraformaldehyde.
Close the container tightly and allow the chemicals to vaporize.
The vapors from these chemicals are effective
in killing molds that have grown into leather, but they give no lasting protection
against future contamination. As the vapors leak out, the chemicals must be
replaced. Before using the shoes or luggage, air them thoroughly.
Wood
Use heat and increase the air circulation to
get mildewed wood as dry as possible. Badly infected wood may need to be replaced,
preferably with wood that has been treated or that is naturally decay-resistant.
Thoroughly clean mildewed surfaces, woodwork
and other wooden parts by scrubbing them with a mild alkali, such as washing
soda or trisodium phosphate (8 to 10 tablespoons to a gallon [3.8 liters] of
water), or with disinfectants, such as a quaternary disinfectant or pentachlorophenate.
Paint and grocery stores and janitors' supply houses sell these products under
various trade names. Rinse the wood well with clear water and allow the wood
to dry thoroughly. Then apply a mildew-resistant paint.
If the mold has grown under the paint or varnish,
remove all the paint or varnish from the stained areas. Then scrub with a solution
containing 8 to 10 tablespoons of trisodium phosphate and 1 cup of household
chlorine bleach to a gallon (3.8 liters) of water. Stronger solutions can be
used if necessary. Wear rubber gloves.
If stain remains, apply oxalic acid (3 tablespoons
to 1 pint (0.47 liters) of water). Caution: The acid is poisonous — handle
carefully. Finally, rinse the surface thoroughly with clear water. Dry well
before refinishing.
Paper and Books
Remove any dry, loose mold from paper with a
clean, soft cloth. If mildewed paper is damp, dry it first in an airy place.
To dry wallpaper, heat the room for several hours or even days to dry the plaster
as well as the paper. Plaster should be dried slowly to prevent cracking.
If mildewed paper is washable, wipe it gently
with a cloth wrung out of thick soapsuds, then with clear water. Take care not
to wet the paper more than necessary. Do not scrub it. Finally pat with a soft,
dry cloth. If stains remain, bleach with a solution of a household bleach, then
sponge with a cloth wrung out of clear water. For small stains, a commercial
ink eradicator may be useful.
"Fan out" pages of books to increase air circulation.
If the books are very damp, sprinkle cornstarch or talcum powder between the
leaves to absorb the moisture. Leave starch or powder on for several hours,
then brush off.
Use of Pesticides
Pesticide use is governed by a federal law and
administered by the Environmental Protection Agency. This law requires manufacturers
to register pesticides and makes it illegal for people to use them except in
accordance with the instructions on the label.
When used as directed, pesticides are safe and
effective; used improperly, they can be injurious to humans, animals and plants.
We caution you to read and follow all directions and precautions on pesticide
labels. Note particularly what the label says on how to.
Store pesticides properly. Apply pesticides
so that they do not endanger humans or livestock or household pets.
Dispose of pesticide containers so that they do not contaminate water or leave
illegal residues. Note all safety precautions that
should be taken. For example:
- Keep pesticides out of reach of children.
- Avoid prolonged breathing of pesticide sprays or dust.
- Wear recommended protective clothing and equipment.
- Avoid swallowing, splashing in eyes, or spilling pesticides on parts of the
body or clothing.
- Know appropriate antidote to use, and have the telephone number of your local
Poison Control Center available for emergencies.
Reviewed by Leon Segal,
ARS Research Chemist, USDA Southern Regional Research Center, New Orleans. Louisiana
70179, and Tyrone L. Vigo, ARS Research Chemist, USDA Textiles and Clothing
Laboratory, Knoxville, Tennessee 37916.
Copyright 2000 University of Missouri. Published
by University Extension, University of Missouri-Columbia.
