Realm of the Mystic Griffin

  "Hundreds of Art Works Damaged By Mildew in Museum Warehouse", reads a New York Times headline from 1988. Mold and mildew damage can happen to the best of us in the art world, but what to do around the studio to prevent our creative world from being invaded by these creepy fungi? Find the answers here, along with several helpful tips for the artist, collector, and those who sell vintage collectables and antiques. Always consult a professional for cleaning items of great value. Some information here is repeated in multiple topic sections, and all information herein must be used at your own risk with best judgement.

 Having lived in the rainforest of Washington State, I've had my fair share of experience with mold and mildew. Over the years I've used each of the methods for cleaning described on this page for a variety of reasons, not only for water and moisture damage issues. I enjoy experiments, and so have put forth some hard tests on these methods. Try to be aware of other situations were this information might be useful, and don't be afraid to try experiments and tests of your own with care and practice materials. A bit of conservation and restoration knowledge is a big help to any artist or collector. Though anything can be restored, sometimes the effort out weighs the value, and you might not be able to save an item from mold damage, especially. Good luck and always try to find fun in what you do.       -- Webmistress Tree

   CONTENTS:

* Causes; What is it?

* Prevention and Control

* General Cleaning

* On Art Supplies and Studio Materials

- About Rubbing Alcohol

- Paint Brushes

* Paintings

- Cleaning A Painting

* Paper

- Cleaning Books

* Dealing with Plaster and Stone

* Fabric & Leather

* Solution Recipes Quick Reference

* Referenced Web Pages for Even More

  Mold and mildew are natural fungi that are everywhere; even in the very air. Mildew can be found as a thin black, green, or sometimes white, growth produced by mold; so mildew is actually mold. Molds are simple plants belonging to the group known as fungi. Fungal infestation will occur only in the presence of an external moisture source, or when the saturation point of nearly 100% Relative Humidity (RH) is approached in combination with still air and moderate temperatures. Mildew will often have a dry powder like fluffy look that seems to sit on top of things, whereas what we think of as typical mold tends to look soaked into a surface and may even seem wet.

  Mold and mildew feed off of biological material to get the energy needed to bloom into a colony. Soil on articles and greasy films, such as those that form from dirty fingerprints, can supply sufficient food for mildew to start growing when moisture and temperature are right. Materials such as plastics, fabrics made from synthetic fibers, and fabrics treated with mildew-resistant finishes won't mildew easily, but soil on the surface can be a starting point for mildew growth. As the organisms grow they cause considerable damage. A powerful musty odor from mildew can cling to affected items. That odor is caused by waste products given off by actively growing molds. Both mold and mildew can cause discoloration, stains, and even rot so that an item cannot be saved. Attics, basements, and closets against exterior walls are places susceptible to changes in temperature, and so to changes in relative humidity (RH). These areas must be surveyed every time it rains or snows, if being used as a studio or art supply storage space.

  There's no need to panic about the dangers of mold toxins, but do treat it with care. Not all molds produce the poisonous substance, mycotoxin; furthermore, molds that can produce mycotoxins don’t produce them in all situations. Unfortunately, when they are present, humans who inhale, ingest, or touch them may have a toxic reaction. Some mycotoxins have been shown to produce serious human health effects, while little is known about the affects of others. The EPA cautions that finding molds in a building does not mean that mycotoxins are also in the building, and even when they are present, the quantities may not be large enough to be health threatening. The freckle like spots often seen on paper and old cloth is called "foxing". These fox spots are the result of a melanin type exudate and not considered harmful to human health in low doses.

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  Relative humidity above 70% encourages mildew or "foxing" on paper. If the humidity in your area exceeds 70% for periods of the year, dehumidify or air-condition rooms where works of art are hanging. Avoid hanging works of art on damp walls. Very dry conditions, below 30% relative humidity, may encourage brittleness of paper, and should also be avoided. For furniture and wooden artifacts the "optimal" environment is about 40º Fahrenheit with roughly 50% RH.

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  To wash mold and mildew out of most items, scrub with a mixture of 1 part household bleach to 3 parts water. Don't use hot water with bleach because it stops the action you want; use cool or tepid water. Rinse twice with warm water and allow to fully dry. Never mix liquid chlorine bleach with ammonia or products containing acids such as toilet bowl cleaners, rust removers, or vinegar, or use for items gathered from the ocean. To do so will release hazardous gases. Chlorine bleach can damage some plastics, aluminum, or chipped enamel surfaces. Test a small spot first before fully treating with bleach. If bleach cannot be used, try an all-purpose household cleaner that is safe for that surface, or other method.

Another method; lightly paint the affected area with a solution of hydrogen peroxide, at 1 part of 3 percent hydrogen peroxide (common household) to 5 parts of water, and then let the sun shine on the item for a while. Rubbing alcohol does kill mold spores, but remember that it is a solvent, (read further for more about rubbing alcohol).

  Check in all the creepy crawler places for mold, but if you really suspect black mold, especially, is in your house call a professional to check. They use masks and safety gear you probably don't have on hand. Some mold is very dangerous. A little bit, on a wall for example, can be treated with household bleach as described above. After cleaning, paint the affected area with a product such as "Kills" to prime for new wall paint. On a very fine wall mural or fresco, I often begin with a coat of Kills incase anything from the wall surface that I missed in cleaning may try to transfer through. Surfaces painted with mildew resistant paint can be injurious if children suck or bite on them. Therefore, mildew resistant paints should not be used on interior surfaces such as window sills, playpens, or toys. 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 telephone directory. 

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  Once supplies, such as gesso or paints, are moldy there's no way to save them. Never start a project with musty smelling, or discolored, materials. Throw out all of the material and clean containers and studio surfaces with rubbing alcohol to reduce the risk of further contamination. Tools, such as the stay wet palette, can quickly mold if neglected. Discard contents, wash palette with hot soapy water, and follow with a good rubbing alcohol wipe.

About Rubbing Alcohol:  The #1 studio supply in my personal opinion is rubbing alcohol; it has tons of helpful uses. Don't mix it directly into paint, but when sprayed or dropped onto wet water media paint it can cause lovely resist effects on both paper and canvas. Use it to clean the computer work station, de-grease fingertips and hands, clean glass, soften dried acrylic for cleaning, and it removes oil paint from skin yet isn't as dangerous as turpentine. Rubbing alcohol does kill mold spores, but remember that it is a solvent. It can also be used to clean the back of frames, price stickers from unfinished wood and plaster; rubbing alcohol causes very little swelling to wood, unlike water, and evaporates quickly. Always use care with rubbing alcohol. Don't lean directly over an item you're cleaning with this solvent to avoid hazardous fumes; it can make you pass out!

PAINT BRUSHES:

  Do you have the bad habit of leaving brushes standing in water after having used them? It can ruin brushes and cause mold. Dirt and mold spores can become trapped in the brush hairs. It will transfer to a painting surface in addition to supplies, potentially causing a mold outbreak, or a weakened spot on the painting surface later. Brushes can be cleaned with rubbing alcohol to sanitize, but follow with a good conditioner, (human hair products work for both natural and synthetic fibers). Rinse very well, swish brushes submerged in water, and allow to dry properly.

  Avoid using tap water altogether when painting. Use distilled water, or filter your own at least. Boiling water and allowing it to cool is better than water straight from the tap. If tap water must be used, keep pallet clean, paints fresh, and change the water often. Use the best quality supplies you can afford and good clean metal or stoneware containers, because plastic absorbs everything.

  Never dip brushes or tools directly into a container of medium or paint; ferrules of brushes will retain and pass contaminants on to the substance they're dipped into. Pour paint, gesso, or other medium into smaller dishes or containers, from the main jar. Wipe the lip of the jar with a clean paper towel before replacing the lid. Don't pour unused portions back into the main jar either; it's like eating what's on your plate. If you need more pour more. Eventually you'll get a feel for how much, gesso especially, to pour for a single sitting. To avoid contamination altogether, don't dip brushes or fingers directly into a jar of anything.

* A nasty experiment to try is to gather some old paint brushes and acrylic paint, (works fastest with craft quality acrylics). Get the brushes good and paint-dirty, then swish them in a mason jar of about two inches of regular tap water. Leave it. See how it changes in color, texture, and SMELL after many days. Eventually a goo will develop on the dirty brushes and the water will turn to slime. Those same chemical reactions go on inside a painting, to one degree or another, when unclean water and low resin paint (low quality) are used. 

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(For paper, see Paper section)

  Molds may penetrate the paint deeply, even to the underlying surface of a painting. Clean any painting at your own risk! A professional should be consulted for valuable or insured pieces. To clean a painting or canvas surface NEVER use bleach, and always test a small area first. Mildew will never totally go away from artwork, and so must be managed by RH and temperature once a bloom has happened. The only "cure" for mildew or mold is to clean the surface well and try to keep the environment steady.

  Remove any frame material; mat boards should be replaced and the frame cleaned or replaced as well. Lay the painting flat and mildew side up on a table top. Outdoors is best, and saw horses with a board can be used as a temporary table. Lay an old clean towel or fabric bit down to protect the painting. Use a face mask, or at least tie a cloth (bandana), to cover your mouth and nose. Gloves should be worn for protection and also to avoid spreading mold feeding body oils. Use a vacuum cleaner and a soft brush to gently remove any surface powder, brushing the powder into the vacuum.

  If the mold starts to wet smear, making a worse mess, stop and go on to moist cleaning, because if it isn't already deep into fibers you don't want to push it there. Once dry powder is removed use cotton swabs, not balls, dipped in one part of 3 percent hydrogen peroxide to 5 parts of water. Remember to test a small area first. If paint color comes off onto the swab with only reasonable pressure you might have to consider allowing some paint loss, repair, or trashing the painting altogether. Work a small area at a time with this moist cleaning solution, carefully dabbing and rolling the swab. As soon as a swab is soiled replace it with a clean one. This takes time, but it can be worth the effort for a beloved piece. When the affected area is cleaned, "moist clean" the entire piece as a whole, and then set it in the sunlight for some time. The sunlight will kill any remaining mold spores. Protective and cleaning gear should be thoroughly cleaned and sanitized after each use, or bagged and discarded if the situation was severe. Clothing worn during the handling of mildewed items should be laundered with hot water, well rinsed, and thoroughly dried.

  Rubbing alcohol does kill mold spores, but again, remember that it is a solvent. It can remove or fog a varnish layer on a painting and will dissolve acrylic paint. Use undiluted rubbing alcohol to clean frame glass, but avoid using it on acrylic or other glazing materials. It can also be used to clean mold from the back of frames, the unfinished wood, by allowing it to soak into the grain. Rubbing alcohol causes little swelling to wood, unlike water, and evaporates quickly avoiding further mold growth. For cleaning art dilute a solution of 1 cup denatured or rubbing alcohol to 1 cup water. Always use care with rubbing alcohol. Don't lean directly over an item you're cleaning with this solvent to avoid hazardous fumes, and apply a good hand lotion after prolonged contact with skin.

  On an outdoor wall mural or fresco, I often begin with a coat of a product such as "Kills", after cleaning, to avoid anything from the wall surface transferring through the art. Surfaces painted with mildew resistant paint can be injurious if children suck or bite on them. Therefore, mildew resistant paints should not be used on interior surfaces such as window sills, playpens, or toys.

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  Paper, when environmental moisture is high, degrades at a much faster rate than canvas when contamination has happened. Always remove paper from the offending environment as soon as possible. Exposing paper to sunlight, briefly, will stop mold and mildew growth, but the paper must still be cleaned of any discoloration or powder residue. Some fungi and bacteria produce rust colored spots often seen on the pages of old books or antique linens. These red or brown spots, called foxing, are the result of a melanin type exudate, (not rust), and are generally not harmful to humans. Oxidative bleaching, with hydrogen peroxide, may reduce the stain but will further weaken the cloth or paper. Keep in mind that using moisture of any kind to clean paper can cause discoloration to soak into the fibers even deeper. The portion of paper that is obscured by mildew will be weaker than the unaffected areas. Always try other methods before using liquid on paper. If using the moist cleaning method, don't use as much liquid or saturate the paper to the point of mush. As stated previously in the Paintings section, use cotton swabs with a gentle rolling motion or dab with a cloth.

  Paper can be moistened with diluted alcohol, (1 cup denatured or rubbing alcohol to 1 cup water). Never scrub paper. You might consider using a spray bottle of rubbing alcohol to lightly mist books and paper effected by mild mildew, after brushing clean as described in the Paintings section above. Dry the article thoroughly. For small stains, a commercial ink eradicator may be useful. Paper paintings and prints can be submerged in a bath for cleaning, but that is a "last ditch" extreme method that requires practice and skill to avoid getting nothing but colored pulp! Washing and agitation will increase the chance of rips, tears, and holes. Do some further research before placing a print or painting directly into water.

  Some portions of a badly damaged project, or when using old pieces of paper for a project, can be salvaged and sealed in acrylic gel medium or PVA glue to prevent a future mildew outbreak once the paper is cleaned. When the glue medium is dry it seals up what's inside. Future blooms shouldn't happen.

  Relative humidity above 70% encourages mildew or "foxing" on paper. If the humidity in your area exceeds 70% for periods of the year, dehumidify or air-condition rooms where works of art are hanging. Simply don’t hang works of art on damp walls! Also, very dry conditions below 30% relative humidity may encourage brittleness of paper, and so should also be avoided. Areas in which books, papers, and photos might be stored, such as a study or private library, may require a dehumidifier. If papers are stored in a closed bookcase or cabinet, continuous use of a low-wattage light or chemical dehumidifier such as silica gel, within the case may be helpful. Valuable paper items should be inspected regularly to see if mildew growth is present.

  Remove any dry, loose mold from paper with a clean, soft cloth or paint brush, as described previously. If the paper is still damp, dry it well first. Spread pages of books out like a fan to air. If the books are very damp, sprinkle cornstarch, or talcum powder, between the pages to take up the moisture. Leave starch or powder on for several hours, then brush off using the vacuum and brush method. Fresh DRY coffee grounds will remove the sharp odor of mildew, but may cause staining so don't put it between the pages. If the odor is still strong after grounds have been closed up with the item for some time, then the mildew is still there; expose the affected item to sunlight for a time and clean again if needed.

  For leather book bindings and covers, wipe off the mold. Wipe the leather surface with a cloth dampened with a solution of 1 part denatured or rubbing alcohol to 1 part water. Apply saddle soap or leather conditioner. 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 or texture of the leather. 

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  Set plaster should be dried slowly to prevent cracking. If a plaster sculpture has mildewed, greater care than with paper even must be used. Plaster is easy to re-shape and will dissolve with liquid, which can cause further damage to the art. Pieces that are well sealed can have the mold washed off with warm soapy water, rinsed carefully, patted dry, and exposed to sunlight for a time. Unsealed plaster, and stone too, is more tricky. Because it's absorbent, the mold will likely have seeped into the deeper layers.

  For unpainted or un-sealed plaster, spray small areas at a time with full strength denatured or rubbing alcohol, taking precautions as stated in other sections of this article. Begin just above where mildew begins and work down. The surface of the plaster will darken when the cleaner sinks in; wait only a few seconds to avoid dissolving the plaster as little as possible. Before the alcohol evaporates, spray the same small area a second time. Then swiftly roll a cotton swab until it is dirty; change swabs often. Use care, and gentle dabbing with the swabs. Only very light rubbing motions should be used. The goal is to somewhat sponge the mold out of the plaster pores with the swabs. Plaster that has been sealed after an outbreak of mold or mildew can still later re-bloom UNDER the finish. It should remain un-sealed and in a stable environment; a spot with sunlight would be just fine for display.

  Natural stone can often be soaked in the bleach solution mentioned in the General Cleaning section, followed by soaking in clean hot water to stop the bleaching action. Some stone, such as marble and alabaster, will soften and degrade from bleach so must be cleaned with special methods. Any cleaning can change the finish of stone, so care should always be taken. Test a spot first to see what might happen and change the cleaning method if you think it's required. Most garden statues can safely be cleaned with bleach solution and used indoors. Smaller stones, such as for craft use, can be boiled carefully and scrubbed, or sanitized in a low temperature oven. Don’t put stones or sculpture that might contain metal into a microwave for drying or to sanitize. It’s a machine that heats from the inside out, and so can cause an explosive and dangerous pop! NEVER put stone that has been exposed to chemicals, mold, or mildew in a fish tank or terrarium.

  Some fungi and bacteria produce rust colored spots often seen on antique linens and old fabric. These red or brown spots, called foxing, are the result of a melanin type exudate, (not rust), and are generally not harmful to humans. Oxidative bleaching, with hydrogen peroxide, may reduce a stain but will further weaken the cloth. The portion of the textile that is obscured by mildew will be weaker than the unaffected areas. Moist cleaning with chemicals may cause further damage the fabric, the dyestuff, and/or the finish. If the growth has damaged enough fiber surface, removing the growth will reveal a perceptively damaged and perhaps discolored area. Washing and agitation may increase the likelihood of rips, tears, and holes.

  Attics, basements, and closets against exterior walls are places susceptible to changes in temperature and RH. They are not recommended for textile storage. Man-made synthetic fibers, and fabrics treated with mildew resistant finishes won't mildew easily, but soil on the surface can be a starting point for it to grow.

  For fabric, upholstery, or stuffed articles, sponge lightly with a solution of detergent and warm water after testing for color fastness. If safe for the fiber, fabric, and finish, use a dilute solution of water and liquid chlorine bleach to sanitize, (one teaspoon bleach to one quart of cool water). Apply the solution with a swab directly on the mildew stain. Then dab repeatedly with clean, cool water and blot dry. Avoid excessive rubbing as it may damage the fabric. In working upholstered articles or pillows, get as little water on the surface as possible so the padding and/or filling does not get wet. Keep in a dry, warm area until articles are fully dry.

  Wash mildew stained clothing or smaller articles at once with soap or detergent and water. Rinse well and dry in the sun. If any stains remain, moisten the area with a paste of lemon juice and salt. Then spread item in the sun to bleach naturally. Rinse thoroughly afterwards and dry again or iron. Never use a chlorine bleach on silk, wool or Spandex fabrics. Some vintage fabrics with wash-and-wear or other special finishes may be damaged by chlorine bleaches.

  Another way to remove mildew on upholstered or leather furniture is to wipe it with a cloth moistened with a solution of 1 cup denatured, or rubbing alcohol, to 1 cup water. Dry the article thoroughly. Wipe a leather surface with saddle soap or leather conditioner. Before treating a leather article, test the conditioning spray on a small area where it will not show. Do this to see whether it will change the color or texture of the leather. 

* Basic Household Bleach Cleaning: 1 part bleach to 3 parts cool water

* To Clean Acrylic or Oil Painting: 1 part hydrogen peroxide to 5 parts water

* Art, Paper, Fabric & Leather: 1 cup denatured or rubbing alcohol to 1 cup water

* Fabric, Upholstery, Stuffed Items: 1 teaspoon bleach to 1 quart of cool water

* Stains: Try mixing enough lemon juice into table salt or baking soda to make a paste. Spread paste on affected item and lay in sunlight to dry. Wash paste out after dry.

* "Hundreds of Art Works Damaged By Mildew in Museum Warehouse"; New York Times, 1988 http://query.nytimes.com/gst/fullpage.html?res=940DE3D71F3DF933A25754C0A96E948260&sec=&spon=&pagewanted=1

* Textiles, http://www.si.edu/mci/english/learn_more/taking_care/mnm.html

* Smithsonian Museum Conservation Institute  http://www.si.edu/mci/english/learn_more/taking_care/care_painting.html

* "How to Prevent and Remove Mildew In Relation To The House and Household Furnishings", Publication Number 356-643, August 1996 Virginia State University http://www.ext.vt.edu/pubs/housing/356-643/356-643.html#L3

* http://www.si.edu/mci/downloads/RELACT/paper_deterioration_sources.pdf

* http://www.servpro.com/services/mold/faq.htm

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Contents assembled and written by Tree Pruitt, 2008