PMG Mold and Foxing Remediation

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Photographic Materials Conservation Catalog
Mold and Foxing Remediation for Photographic Materials

Date: Initiated September 2009
Contributors: Luisa Casella, Amanda Maloney, Stephanie Watkins
The Photographic Materials Conservation Catalog is produced by the Photographic Materials Group of the American Institute for Conservation of Historic and Artistic Works as a convenience for the membership. The treatments, methods, or techniques described herein are provided for informational purposes. The reader assumes responsibility for any application results.

Purpose of Mold and Foxing Remediation for Photographic Materials

To maximize the chemical and physical stability of the object during and after remediation technique while minimizing changes in the image, binder, and support from remediation techniques.

Detail of silver gelatin print showing mold damage

Factors to Consider

Effects of Mold and Foxing Remediation

Equipment and Materials

  • Fumehood
  • Mask
  • Nitrile gloves
  • Hazmat suit
  • Plastic bags

Techniques for Mold and Foxing Remediation

Annotated Bibliography

General Information

  • Bailey, H. 2005. Fungal contamination: a manual for investigation, remediation, and control. Jupiter, FL: Building Environment Consultants, Inc.
    • The introduction to this book states, “This work was specifically written to allow workers, laborers, builders, maintenance people, facility managers, and others who may have a minimal scientific background to gain the knowledge and understanding they need to address the investigation (assessment), remediation, and prevention or control of mold as part of their daily duties.” This is a fairly comprehensive book consisting of 389 pages including an index, chapter summaries at the end of each chapter and summaries of guidelines from various government or national groups about the remediation of fungal infestations. The book covers issues related to the classification, structure and life cycle of fungi; identifying problem areas in buildings and how to sample of fungal growth and air quality, health effects, how to organize a team and the steps to take during mold remediation in a building. It provides good clear descriptions of what mold is and how it should be handled; however, it is written for disaster recovery of occupied buildings rather than for cultural materials. It does include a couple of short sections on how to handle library materials (pages 172-173), paper objects, and photographs (pages 214-215) that have been affected by mold or water-damage. The section on antimicrobials (pages 196-200) defines and differentiates between fungicides, disinfectants, fungistats, and sporicides, giving examples of each and discussions of proper use. This book provides a good resource for disaster planning in an emergency mold remediation project in a cultural institution.
  • Mandrioli, P., G. Caneva, and C. Sabbioni. 2003. Cultural heritage and aerobiology: methods and measurement techniques for biodeterioration monitoring. The Netherlands: Kluwer Academic Publishers.
    • This book presents a scientific examination of how airborne biological particles affect cultural material in a variety of indoor and outdoor environments, as well as how to monitor these particles to assess risk. It discusses specific types of materials and environmental factors that are prone to biodeterioration. There is also an in depth review of sampling techniques to identify the amount and kind of microbes present. This book offers helpful and detailed discussions of the affect of bioaersols on the specific environments of libraries and archives, museums, churches and hypogea.
  • Nyberg, S. 2002. Invasion of the giant mold spore. Solinet preservation leaflet. http://cool.conservation-us.org/byauth/nyberg/spore.html (accessed Jan 2010).
    • This article provides a simplified summary of what mold is and details about how to detect and prevent it. The author discusses several treatment options for dealing with moldy objects. She does not recommend using chemical treatments, but does provide a list of chemicals that have been used as fumigants in the past along with their risks to human health and certain materials.
  • Valentin, N. 2003. Microbial contamination in museum collections: organic materials. In Molecular Biology and Cultural Heritage, ed. C. Saiz-Jimenez. The Netherlands: Swets & Zeitlinger. 85-91
    • This article provides a brief literature review of non-chemical means of arresting or eliminating microbial growth in collection of organic materials. It has a chart of the most commonly found species of fungi and bacteria in museum collections. The author stresses the importance of controlling the water activity of an object as well as the relative humidity of the air. Most microbes will grow on organic objects with a water activity of 0.6 to 0.98. The author also advocates for using low temperatures (-20 ºC), nitrogen gas, and good ventilation as practical means to arrest microbial growth.

Biology of Fungi

  • Caneva, G., M. P. Nugari, O. Salvadori. 2008. Plant biology for cultural heritage: biodeterioration and conservation. Los Angeles: Getty Publications.
    • This book addresses the biological processes of fungi, bacteria, algae, and lichens; focusing on how they effect of a variety of cultural heritage material. It is the first volume of a two volume set and it deals primarily with how and why biodeterioration occurs and what can be done to prevent it. The second volume, which has not been translated into English, deals more specifically with treatment. However, there are some treatment suggestions in this volume. It discusses the biology and environment in great detail with useful figures and graphs. The book has detailed descriptions of biodeterioratin as related to specific substrates, such as paper, photographs, leather, glass, and metal among many others found in cultural heritage collections. There are also useful sections on prevention and remediation for a variety of specific materials.
  • Christensen, C. 1965. The molds and man: an introduction to the fungi. 3rd ed. New York: McGraw Hill.
    • This book provides easy to understand and very comprehensive introduction to the biological functions of a variety of fungi. Much of the book has an agricultural focus, discussing the benefits and harms caused by fungi to plants and animals. There is one section that deals with fungi in buildings, but none that specifically addresses heritage material. There is an extensive index that could be helpful for looking up traits of a known fungus.
  • Florian, M-L. 1997. Heritage eaters: insects & fungi in heritage collections. London: James & James.
    • This book provides a description of the biology of fungus and insects as a way to control their presence in heritage collections. The first half of the book deals with insects and the second half (pages 111-153) with fungi. She discuses the different stages of development of the conidia (spores) and what circumstances will cause them to germinate. She stresses the importance of good housekeeping to prevent spores from settling on objects. The author includes a clear discussion of the relation of relative humidity to equilibrium moisture content and water activity. This is an important concept because really it is the moisture content of the substrate that provides the favorable moisture environment for germination of the conidia. Many sections of the book contain informative literature reviews on the topics under discussion. She discusses remediation techniques such as freezing, dehydration, fungicides, irradiation, and anoxic environments.
  • Florian, M-L. 2002. Fungal facts: solving fungal problems in heritage collections. London: Archetype Publications Ltd.
    • The majority of this book concentrates on explaining what fungi are and how they effect different types of material. Chapter 7 provides useful guidelines for treatment of objects affected by mold. The author concludes the book with discussions about sampling, disaster recovery, and implementing appropriate environmental controls.

Health and Safety

  • 2001. Mold and fungus. Hazardous Materials Assessment Inc., San Loreando. http://www.asbestos.org/mold/mold_frames.html (accessed Jan 2010).
    • This fact sheet is directed toward the general public facing problems with mold infestations in their homes. It provides bulleted lists of information including the types of mold that can cause health problems; common causes of increased moisture in a home that will cause mold outbreaks; and symptoms of mold exposure. The protective measures they suggest are wearing a N95 or TC-21C particulate respirator, gloves, clothing that can be discarded after clean up, work over short time spans to limit exposure, and to keep the area well ventilated. They also recommend cleaning procedures suitable for a private home, but not for remediation of mold on cultural artifacts. They consist primarily of disposing of porous objects that have been contaminated with mold, cleaning the affected area and any non-porous objects with soap and water, followed by a wet vacuum, and finally wiping down all surfaces with a 10% solution of household chlorine bleach.
  • 2003. A brief guide to mold, moisture, and your home. Office of Air and Radiation Indoor Environments Division, Environmental Protection Acency. http://www.epa.gov/mold/moldguide.html (accessed Jan 2010).
    • This guide briefly talks about mold problems in private homes and stresses the importance of controlling moisture ingress to prevent mold outbreaks. If the area of mold is greater than ten feet square, is in a heating/ventilation/air conditioning (HVAC) system, or is caused by sewage they recommend hiring a contractor to deal with remediation. If the area is less than ten feet square they give guidelines to follow for clean up. They recommend wearing a N-95 respirator for particulate matter, wearing long gloves, and goggles that do not have ventilation holes. The EPA recommends using a mild detergent to clean mold and suggest using chlorine bleach only if someone who is at risk (infant, elderly, or immune-compromised) will be occupying that area. This is followed by a mold prevention section that gives tips for reducing moisture in a private home.
  • 2009. Comments and suggestions from the American Industrial Hygiene Association on H.R. 1269. American Industrial Hygiene Association. http://www.aiha.org/news-pubs/govtaffairs/Documents/news05_HR1269-Conyers-Comments-05-04-05.pdf - (accessed Jan 2010).
    • This document is a reaction from the American Industrial Hygiene Association (AIHA) to the House Resolution 1269, an amendment to the United States Toxic Substances Safety Act proposed in 2005 (http://www.govtrack.us/congress/bill.xpd?bill=h109-1269). This amendment would classify mold and fungi as toxic substances subject to regulation and federal support programs. This document is particularly interesting in that the AIHA disagrees with the principle tenant of the bill, that certain molds should be classified as “toxic”. The AIHA states that while there are molds capable of producing mycotoxins, there has not been a clear link between these and adverse health affects. The AIHA says the definition of “toxic mold” is too broad and in reality adverse health affects are more akin to allergic reactions than exposure to toxic substances. Through out the document the AIHA also suggests that the Occupational Safety and Health Administration (OSHA) and the National Institute for Occupational Safety and Health (NIOSH) be listed along with the federal agencies given authority in defining potential threats and courses of action due to fungal infestations. The AIHA disputes the bill’s tendency to generalize because actual health threats depend both on the specific species of mold as well as the individual exposed to the mold.
  • Hardin, B. PhD, B. Kelman PhD, DABT, A. Saxon, MD. 2002. Adverse human health effects associated with molds in the indoor environment. American College of Occupational and Environmental Medicine. http://www.acoem.org/guidelines.aspx?id=850# (accessed Jan 2010)
    • Mold can affect people through three processes: allergy, infection, and toxicity. The most common allergenic indoor molds are Penicillium and Aspergillus; these are also the types most usually found on organic objects. About 10% of the population will have allergic reactions to these fungi. The authors also discuss some uncommon allergic symptoms caused by fungi, and say that often allergic reactions to dust mites or bacterial growth are misdiagnosed as fungal allergies. The molds which can cause serious infections in otherwise healthy individuals are: Blastomyces, Coccidiodies, Cryptococcus, and Histoplasma. The population who is most at risk for infection are people receiving chemotherapy or immunosuppressive drugs, AIDS pateients, and patients with uncontrolled diabetes. The authors stress that there is not evidence that inhaled mycotoxins have adversely affected the health of individuals in the indoor environment. Mycotoxins are large molecules and are non-volitile, but can be stirred up and inhaled as an aerosol. This aerosol exposure only becomes serious when it happens on a frequent basis in high doses, such as with agricultural workers moving affected grain. The authors put the point at which fungal growth can occur at 40% relative humidity.
  • Light, E. 2003. “Toxic mold” – the future of industrial hygiene or just another IEQ “flavor or the month”?. ABIH News (November). American Board of Industrial Hygiene. http://www.abih.org/downloads/nl03-11.htm (accessed Jan 2010)
    • The premise of this article is that there is little evidence that indoor mold should be handled as a toxic substance. The author thinks that there is a great deal of money being spent on litigation and recovery/clean up of mold that is scientifically unfounded.
  • Money, N. 2004. Carpet monsters and killer spores: a natural history of toxic mold. New York: Oxford University Press.
    • This book discusses some of the worse case scenario effects of mold infestations in homes and businesses.
  • Rosol, M. 1994. Book mold data sheet. Acts Facts 8 (10): 3.
    • This review of the mold remediation guidelines published by The Center for Conservation of Art and Historic Artifacts in 1994 is mostly favorable. However, the author is careful to point out that using a water filtered vacuum, as recommended in the guidelines, will not actually filter out mold particles and only HEPA vacuums should be used.
  • Salkinoja-Salonen, M. S., J. Peltola, M. A. Andersson, and C. Saiz-Jimenez. 2003. Microbial toxins in moisture damaged indoor environment and cultural assets. In Molecular Biology and Cultural Heritage, ed. C. Saiz-Jimenez. The Netherlands: Swets & Zeitlinger. 93-105.
    • This article provides information on the classes of toxins produced by microorganisms and the specific species of fungi or bacteria likely to produce them. Toxicity is difficult to predict because different strains of the same species may produce different toxins, several toxins, or none at all. Many toxins can be absorbed through the skin by direct contact and the authors recommend covering exposed skin. They also recommend wearing cotton gloves under nitrile or latex gloves as this will help prevent sorption of hydrophobic toxins, and that clothes should be washed at 60 ºC or higher with detergents that have enzymes. Of course, they also advocate for use of respirators, good ventilation, and caution not to stir up too much aerosol during the treatment of materials affected by microorganisms.

Disaster Recovery/Prevention

  • Chicora Foundation. 1998. Mold: understanding the problem and recovering safely. Columbia, SC: Chicora Foundation, Inc.
    • This informational booklet offers general advise on dealing with mold. It identifies the main types of mold found in library collections as being of the Penicillium, Fusarium, Aspergillus, and Cladosporium families and identifies the biology of fungi. It briefly addresses causes of mold outbreaks (moisture, poor housekeeping, etc.) and health effects. It has a section with information on how to contact professionals for dehumidification or clean up after mold has been discovered.
  • Dicus, D. H. 2000. One response to a collection wide mold outbreak: how bad can it be: how good can it get? Journal of the American Institute for Conservation 39 (1): 85-105.
    • This article provides a very useful and candid account of disaster recovery efforts following a mold outbreak at the Detroit Historical Museum. Some useful observations were that objects in buffered microclimates had significantly less mold growth, soiled surfaces had the most mold growth, and none of the Tyvek wrappers showed mold growth. Stabilizing the environment is the first key step to remediation. It is important to get an air handler with a reheat function as well as a dehumidifier, so that temperature and relative humidity can both be controlled. A 70% isopropanol solution was used for disinfecting work areas and a 10% Clorox bleach solution was used to clean tools and brushes, preferably in hot water. The HEPA vacuums used were the Royal Classic Power Team canister vacuum, model 4650, the Royal Pro Series canister vacuum, and the Nilfisk GS80. All were filtered to 99.9% efficiency with a particle size of 0.3 µm. All personal were required to wear particulate respirators, gloves, and cotton coveralls. Shoes were to be wiped down with Handi-Wipes after exiting the work area.
  • Florian, M-L. 2000. Aseptic techniques: a goal to strive for in collection recovery of moldy archival materials and artifacts. Journal of the American Institute for Conservation 39 (1): 107-115.
    • Florian explains the life cycle and structure of conidia producing molds and discusses the health and safety precautions necessary to prevent the further spread of mold during remediation. She names the commonest species as Alternaria, Cladosporium, Aspergillus, and Penicillium. She also discusses standards for sampling, either via the air or the surface of the effected object, and the pros and cons of the different methods. A 70% solution of ethyl alcohol or isopropyl alcohol is recommended as a disinfection method for all materials that come in contact with the mold.
  • Strang, T. and J. Dawson. 1991. Controlling Museum Fungal Problems. Technical Bulletin No. 12. Ottawa, Canada: Canadian Conservation Institute.
    • This bulletin takes a holistic approach to controlling fungal problems looking at the building envelope, environment, and good housekeeping. When the environment is difficult to control they suggest using heat sealed polyethylene bags. For clean-up they recommend vacuuming, using fume hoods or respirators and protective clothing. The only fungicides they recommend are 70% alcohol solutions, orthophenylphenol (soluble in organic solvents) , and sodium orthophenylphenate; which can be swabbed or sprayed on. There is a brief review of several other fungicides.
  • Tsai, S., C. Yang, P. Moffett, and A. Puccetti. 1999. Comparative studies of collection efficiency of airborne fungal matter using Andersen single-stage sampler and Air-O-Cell cassette. In Bioaerosols, fungi, and mycotoxins: health effects, assessment, prevention, and control, ed. E. Johanning. Albany, NY: Eastern New York Occupational and Environmental Health Center. 457-64.
    • This study found that there was not good correlation between the amount of fungal populations detected by the Andersen sampler compared to the Air-O-Cell cassette. The Air-O-Cell cassette detected higher amounts of fungal colonies than the Andersen sampler when run at the same flow rate for the same length of time.
  • Zorn, S., K. Liedtke, S. Dobrusskin, M. Koch. 2002. Pilot photography resoration project in Dresden from November 23-29, 2002, trans. O. Dann. Unpublished.
    • This paper describes the disaster recovery steps after a flood affected the Sächsischen Zeitung Archives in Dresden. Most materials were frozen as soon as they could be recovered, before they were cleaned, and were then systematically thawed and cleaned in a baths of distilled water, water and a wetting agent, a 1:1 distilled water and ethanol solution, or a 96% ethanol solution. Some lantern slides that were not frozen had sever mold growth they were scanned to try to preserve as much information as possible.

Chemical Treatments

  • Ali, Y, D. J. Dolan, E. J. Fendler, and E. L. Larson. 2001. Alcohols. In Disinfection, sterilization, and preservation. 5th ed. Edited by S.S. Block. Philadelphia: Lea and Febiger: 229-253.
    • This article is primarily written by and for those in medical professions. It begins with a history of the use of alcohol as an antiseptic. Alcohols are not sporicidal (they can inhibit germination, but this can be reversed), but are effective antimicrobial agents against a wide variety of microbes including fungi in its vegetative form. Alcohols attack microorganisms by causing protein coagulation/denaturation as well as interfering with cellular metabolism. For this to be effective some water must be present, pure alcohol can have a dehydrating effect, but will not be as antimicrobial as that with some water content. Chain length also affects the antibacterial effects. Tests have shown that propan-1-ol is the most effective water soluble alcohol, though ethanol is more commonly used.
  • Baer, N. S. and M. H. Ellis. 1988. Conservation notes on thymol fumigation. The International Journal of Museum Management and Curatorship 7: 185-188.
    • Thymol is a fungicide that has been commonly used in paper conservation. It could be incorporated into wheat starch paste to prolong its usability. Paper objects were also exposed to tymol fumes or were housed with thymol impregnated papers to deter mold growth. By the time of the writing of this article, in 1988, the safety of the use of thymol was coming into question, and Baer reviews some of the recent literature about the use of thymol. Tymol posses a threat to the health of the conservators using it, as an irritant and possible carcinogen. It also has been seen to soften resin based media and coatings on objects, as well as to soften and yellow acrylic glazing. There have been instances of it recrystallizing on the surface of a treated object. The author brings up the need for more research to be done on o-phenyl phenol (OPP) as a possible substitute for thymol, but concludes with saying proper environment is really the best prevention.
  • Block, S. S. 2001. Peroxygen Compounds. In Disinfection, sterilization, and preservation. 5th ed. Edited by S. S. Block. Philadelphia: Lea and Febiger: 185-204.
    • This article discusses the history of use and properties of peroxygen compounds as disinfectants. It has been found that hydrogen peroxide at 10-25% concentration has sporacidal properties, and is a good disinfectant at concentrations as low as 3%. Hydrogen peroxide is a safe disinfectant and occurs naturally in honey, milk, and the mucus membranes of our mouths. Hydrogen peroxide can form hydroxyl radicals, the strongest known oxidant. Tests have shown it is not significantly affected by change in pH, but will increase in efficacy with increased temperature and concentration. It can be applied as a liquid, gas, or plasma. The properties and applications of peracetic acid are also discussed.
  • Calnan, C. 1985. Fungicides used on leather. Northhampton, UK: The Leather Conservation Centre.
    • This short publication summarizes the properties of fungicides commonly used by the leather industry and those used in conservation. There are several tables and appendixes that provide information on specific fungicides. The application of fungicides to leather is briefly discussed and it is concluded that more research needs to be done before industry fungicides can be used in conservation applications. No specific fungicides are recommended above others, but a comprehensive list is presented.
  • Dychdala, G. R. 2001. Chlorine and Chlorine Compounds. In Disinfection, sterilization, and preservation. 5th ed. Edited by S.S. Block. Philadelphia: Lea and Febiger: 135-157.
    • This article is primarily written by and for those in medical professions. It begins with a history of the use of chlorine containing compounds as disinfectants. Chlorine is a very strong oxidizer. The exact mechanism of its biocidal action is not fully understood, but is thought to relate to the production of hypochlorous acid in aqueous solution. Thus chlorine solutions at a high pH is less effective than at a low pH. Raising the concentration of chlorine in solution or the temperature of the solution will also increase its biocidal activity. Different strains of microbial organisms will have different susceptibilities to the action of chlorine. The author includes specific discussion of the properties of a variety of chlorine containing compounds.
  • Gillatt, J. 1991. Methods for the efficacy testing of industrial biocides – 1. Evaluation of wet-state preservatives. International Biodeterioration 27: 383-394.
    • This article examines the effectiveness of industrial biocides in five different substances: an emulsion paint, a metal working fluid, a starch-based adhesive, a bituminous emulsion, and a ready-mixed ceramic tile adhesive. The idea of wet-state resistance pertains to the material in solution before it has formed a film. It was found that a proprietary combination of heterocyclic compounds in a concentration of 0.10% completely stopped growth in the starch based adhesive and significantly stopped growth in the emulsion paint. This study does not directly correlate to uses in conservation, but does provide an avenue for further research.
  • Goddard, P. A. and K. A. McCue. 2001. Phenolic Compounds. In Disinfection, sterilization, and preservation. 5th ed. Edited by S. S. Block. Philadelphia: Lea and Febiger: 255-281.
    • This article begins with a history of the production and use of phenolic compounds as antimicrobial agents. The effectiveness of the phenolic compound is dependent on the type and quantity of substitutions on the phenol ring. Thymol and o-phenylphenol are the phenolic compounds that have historically been used in conservation, this article written primarily for a medical audience offers insight into other compounds that may be safer and more effective, though much research needs to be done on the application of these in conservation.
  • Gustafson, R. A., I. R. Modaresi, G. V. Hampton, R. J. Chepesiuk, G. A. Kelley. 1990. Fungicidal efficacy of selected chemicals in thymol cabinets. Journal of the American institute for Conservation 29 (2) 153-168.
    • This study tested the efficacy of eight different fungicides and found that only thymol and paraformaldehyde helped to prevent regrowth of mold cultures with paraformaldehyde performing slightly better in the prevention of conidia germination. However, the authors concluded that the health risks associated with paraformadehyde made it too hazardous to recommend. They also found ortho-phenylphenol, which had been recommended as a substitute for thymol, to be completely ineffective. They concluded that manual removal of the mold and environmental controls to be the most effective and safe procedures for remediation and prevention of mold growth.
  • Haines, B. 1985. Fungicides and environmental controls for leather. In Recent Advances in Leather Conservation. Washington D.C.: Foundation for the American Institute for Conservation.
    • The paper presents the results of a study comparing thymol and o-phenyl phenol (OPP). Neither fumigant was able to stop growth of the test species. The author concludes the only way to stop fungal growth is to maintain an adequate environment and good housekeeping.
  • Haines, J. H. and S. A. Kohler. 1986. An evaluation of ortho-phenyl phenol as a fungicidal fumigant for archives and libraries. Journal of the American Institute for Conservation. 25: 49-55.
    • The paper presents the results of a study comparing thymol and o-phenyl phenol (OPP). Neither fumigant was able to stop growth of the test species. The author concludes the only way to stop fungal growth is to maintain an adequate environment and good housekeeping.
  • Isabell, L. H. 1997. The effects of thymol on paper, pigments, and media. Abbey Newsletter 21 (3). http://cool.conservation-us.org/byorg/abbey/an/an21/an21-3/an21-308.html (accessed February 2010)
    • This paper discusses the properties of thymol and its affect on paper, pigments, and media. The author concludes that thymol provides no lasting protection against fungal growth, and can discolor paper, parchment, inks, and organic pigments. The exact mechanism of this discoloration is unclear, though some ideas are proposed. The author recommends mechanical removal or immersion in ethanol as two possible alternatives for mold removal.
  • Motylewski, K. 1994. Non-toxic fumigation and alternative control techniques for preserving cultural/historic properties and collections: notes on a conference. From the conference Pest, Insect and Fungus Management: Non-toxic Fumigation and Alternative Control Techniques for Preserving Cultural/Historic Properties and Collections. Technology and Conservation at the Harvard University Environmental Health and Safety Department. Cambridge, MA.
    • This paper provides brief summaries of a series of lectures given by professionals in the fields of conservation, entomology, and engineering. There is an interesting diversity of opinion on several topics such as the efficacy of anoxic environments on fungi and the safety of the use of fumigants. Some new ideas had to do with using borates, which are naturally occurring chemicals that prevent insect and mold infestations in some types of wood, and have been used for several decades in Australia and Europe.
  • Nugari, M. P. and O. Salvadori. 2003. Biodeterioration control of cultural heritage: methods and products. In Molecular Biology and Cultural Heritage, ed. C. Saiz-Jimenez. The Netherlands: Swets & Zeitlinger. 233-242.
    • This article provides a summary of mechanical, physical, and chemical means of treating microorganisms on objects in cultural heritage collections. Mechanical techniques include manual removal and vacuuming. These techniques do not result in full removal of the fungal bodies and can sometimes result in damage to the object, but are recommended as a first step when appropriate, then folloed with physical or chemical removal as well. Physical methods consist of microwave, gamma, beta, Röntgen, X-ray, far ultraviolet radiation, as well as heating and freezing. Of the irradiation methosds, the authors feel that microwave radiation shows the most promise for use, but needs more research. The other forms of irradiation have been shown to cause harm especially to cellulosic or proteinacious materials. The most common biocide used currently are the quaternary ammonium salts (QUATs) followed by o-Phenylphenol (OPP). The author also review fumigants commonly used in the past cautioning against there use today. Unfortunately, viable fungal growth will still be present even after weeks and months of exposure in anoxic environments, so this is not a recommended treatment. In the application of any of these techniques careful consideration needs to be given to the specific substrate and the method and duration of application. There is no totally safe totally successful method.
  • Ponce-Jimenez, M. D. P, F. A. Lopez-Dellamary Toral, H. Gutierrez-Polido. 2002. Antifungal protection and sizing of paper with chitosan salts and cellulose ethers: part 2, antifungal effects. Journal of the American Institute for Conservation 41 (3). 255-268.
    • This article describes a study comparing resilience to fungal attacks of papers sized with cellulose ethers and paper sized with chitosan salts. After the sample papers were sized they were inoculated with several common fungal cultures, which were allowed to germinate, then they were sterilized in alcohol and the zero-span tensile strength was used to evaluate deterioration. The chitosan salts did provide slightly more protection to the paper samples. The authors conclude that this is probably due to a mechanical barrier formed around the fibers by the chitosan, and that further testing is needed.
  • Residori, L. and P. Ronci. 1986. Preliminary study on the use of ethylene oxide for the sterilization and disinfestations of books and documents. Paper Conservator, 10: 49-54.
    • This paper examines the safety and effectiveness of ethylene oxide fumigation. At the time the study was conducted there was no regulatory legislation in Italy for the use of ethylene oxide. The authors found that ethylene oxide could be detected outside of the fumigation chambers; that there was residual ethylene oxide present in treated objects, and that the treatment was not always effective.
  • Smith, R. D. 1986. Fumigation quandary: more overkill or common sense? Paper Conservator, 10: 46-47.
    • This article review non-chemical means of controlling microbes and pests in library collections. The author recommends freezing, CO2 gas, and vacuum pressure.
  • Weaver-Meyers, P. L., W. A. Stolt and B. Kowaleski. 2000. Controlling mold on library materials with chlorine dioxide: an eight-year case study. Abbey Newsletter 24 (4). http://cool.conservation-us.org/byorg/abbey/an/an24/an24-4/an24-402.html (accessed Jan 2010).
    • This article discusses the success that the Oklahoma Libraries have had using chlorine dioxide as a fungicide. The authors state that it is safer to use than most commonly used fungicides and has been approved for use in drinking water by the EPA. There were three ways in which chlorine dioxide has been employed: in solution wiped on affected objects and furniture; as a fog for overall infestation; and in time release packets, Aseptrol, for overall infestation.
  • Wellheiser, J. G. 1992. Nonchemical treatment processes for disinfestations of insects and fungi in library collections. Munich: K. G. Saur.
    • This report discusses the processes currently under development for nonchemical disinfection. It looks largely at research from the fields of agriculture, health car, and the food industry. The author reviews the chemical treatments that have been used historically and then discusses possible non-chemical treatments in detail. The non-chemical treatments discussed are: deep freezing, high-energy (gamma) irradiation, low-energy (microwave) irradiation, modified atmospheres, and she also briefly touches on mechanical removal, heat, housing, biological controls (phermones, predators, sterility), environment, and maintenance. Unfortunately, the gamma irradiation is the only truly effective treatment for fungi, and it usually causes unacceptable levels of damage to the object being treated.

Studies of Mold on Books and Paper

  • Arai, H. 1993. Relationship between fungi and brown spots found in various materials. In Biodeterioration of Cultural Property, Proceedings of the 2nd International Conference, Yokohama, Japan. 320-336.
    • This paper is an exploration into the causes of brown spots on paper, silk textiles and wall paintings commonly known as “foxing”, using analytical instrumentation such as Secondary Electron Microscopy – Energy Dispersive X-ray Spectroscopy (SEM-EDS). SEM can provide an image magnified over ten thousand times and was used in this study to look for evidence of fungal structures in foxing spots. EDS can perform elemental analysis of the sample and was used to look for the presence of iron thought to be associated with the foxing spots. The author believed his experiments showed that fungus, not iron, was the main cause of foxing. Some samples were cultured and identified as Asperigillus penicilloids Spegazzini and Eurotium herbarioru. The author proposed that foxing could be caused by a Maillard reaction between the sugars from the cellulose broken down by the fungi and the amino acid products of the metabolism of the fungi. He also performed Thin Layer Chromatography (TLC) on extracts from the foxed areas to classify the saccharides and amino acids present.
  • Arney, J. S. and L. B. Pollack. 1980. The retention of organic solvents in paper. Journal of the American Institute for Conservation 19 (2): 69-74.
    • This paper presents the results of an experiment using gas chromatography to detect the residual amount of organic solvents and sublimed thymol retained in samples of rag paper and newsprint thus treated. The test samples were allowed to absorb liquid ethanol, methanol, acetone, ethyl ether, methylene chloride, chloroform, carbon tetrachloride, or toluene for 15 minutes; or were exposed to thymol vapors for one week. The findings for all paper samples was that solvents were replaced by water when allowed to equilibrate over night at 20 °C and 50% relative humidity. In the absence of humidity the solvents remain in the paper to varying degrees. The fact that thymol does not remain in the paper at standard conditions means that it cannot protect a paper from biological deterioration. However, it is a benefit that thymol does not remain in the paper as it is subject to oxidative decomposition that results in browning and is known to have a softening effect on certain media and coatings.
  • Clapp, A. F. 1987. Curatorial care of works of art on paper. 4th ed, New York: Nick Lyons Books.
    • This book is written as a general resource for the care of paper objects. There are some specific sections that deal with mold growth (pages 28-33; 46-). The author focuses on the need to keep an environment below 70% relative humidity and make sure there is good circulation of air. She briefly describes how to construct a fumigation chamber, as well as techniques using ethylene oxide, naphthalene, paradichlorobenzene, thymol, salicylanilide, copper 8-hydroxy-quinolinate, prthophenyl phenol, pentachlorphenol, “leather protector”, “Cire 212”, and “Xylamon-Clear”. It is interesting to know what historically has been used; however, these fungicides have now been determined too hazardous to use for both human health and the preservation of the object.
  • Craig, R. 1986. Alternative approaches to the treatment of mould biodeterioration – an international problem. The Paper Conservator, 10: 27-30.
    • This paper discusses some of the results of a 1983 survey that was sent to 36 archives in the United Kingdom. Thymol was by far the preferred fumigant of the time, followed by ethylene oxide, carbon dioxide, and lastly gamma irradiation. The author also notes that bacterial growth can be misidentified as fungi and may require a different approach for remediation. Controlling the environment is suggested. The benefits of the kiri wood boxes that have been used for centuries to store scrolls in Japan were also discussed. They offer effective prevention against fungal attack because they provide a tight seal and good buffering against the extreme seasonal changes encountered in Japan.
  • Di Bonaventura, M. P., R. De Salle, J. Bonacum, R. Koestler. 2003. Tiffany’s drawings, fungal spots and phylogenetic trees. In Molecular Biology and Cultural Heritage, ed. C. Saiz-Jimenez. The Netherlands: Swets & Zeitlinger. 131-135.
    • This article describes techniques used to identify fungal spots without culturing the fungi. Polymerase chain reaction was used to amplify the information extracted from the DNA and direct DNA extraction was also used. The authors found many different species of fungi on the Tiffany drawings examined. Most were from the genera Cladosporium, Madurella, Mycosphaerella, and Thielavia.
  • Ellis, M. H. 1987. The care for prints and drawings. Nashville: The American Association for State and Local History.
    • This book provides general care guidelines for drawings and prints. Several sections deal with the prevention and removal of mold. Pages 41-49 deal with detection and removal of active mold and foxing stans. The author discusses the role of humidity in a proper storage environment and how to set up relative humidity monitoring and dehumidifiers (pages 161-166). At the end of this section she brings up fumigation with thymol or naphthalene. She is careful to add that fumigation is not a long term preventive treatment and that objects treated with thymol can grow mold again if they are placed in inappropriate environments and that thymol treatments are not appropriate for objects with oil paint, varnish, synthetic resins, or parchment. Appendix 3 (pages 236-241) provides instructions for building and using a thymol cabinet and is full of cautions about the use of this method.
  • Florian, M-L. 1996. The role of conidia of fungi in fox spots. Studies in Conservation, 41 (20): 65-75.
    • This article looks at the possible causes of foxing in paper and suggests that foxing stains are caused by fungi introduced in the drying of the paper or the binding of the books, and may have been present in the felts used for drying. The author focuses on book papers from the sixteenth to the twentieth century that have foxing stains without a central spot and that are the same surface texture as the paper, sometimes termed “snowflake” foxing. Samples were viewed with SEM-EDX and transmitted light photography, where they were dyed to differentiate the cellulose in the paper from the protein in the fungi. The state of development of the fungi found in the foxing spots suggested that they had germinated in situ and were not deposited from airborne particles. They also always occurred under any printing on the page. Florian concludes that the autoxidation of lipids from the conidia could form a foxed color and a fluorescent product
  • Kowalik, R. 1980. Microbiodeterioration of library materials part 1: chapters 1-3. Restaurator 4: 99-114.
    • This article discusses bacteria, actinomycetales, fungi, yeasts, and algae in relation to biodeterioration of library materials. Many metabolic products of these microorganism are acidic and can damage inorganic as well as organic materials.
  • Kowalik, R. 1984. Microbiodeterioration of library materials part 2: microbiodecomposion of auxiliary materials chapters 5-9. Restaurator 6: 61-115.
    • In this follow up to Kowalik’s 1980 article, the affect of microorganisms on specific materials found in library collections is discussed, as well as the control of microorganisms using biocides. The author cultured samples of fungi and bacteria from various materials and tested the effectiveness of certain biocides. The fungi investigated were cultured from: adhesives, wax seals, inks, paints, metals, and glass; and over two dozen different chemical biocides were tested on these and the results reported. The author does mention that most of these biocides do pose a threat to humans and discusses their toxicity. He closes with a discussion of the prevalence of different species of molds and the potential human health threats posed by them.
  • McCrady, E. 1999. Mold: the whole picture. Pt. 2, Assessment of Mold Problems. Abbey Newsletter 23 (5). http://cool.conservation-us.org/byorg/abbey/an/an23/an23-5/an23-502.html (accessed Jan 2010)
    • This follow up to the previous article gives more details on how to detect mold and what a mold remediation project will entail. The author emphasizes health and safety issues. She goes into detail about sampling procedures and methodology.
  • Szczepanowska, H. 1986. Biodeterioration of art objects on paper. Paper Conservator, 10: 27-30.
    • This article offers a good introduction to the biology of mold as it effects works of art on paper. The author also offers treatment advise for techniques of manual removal. One interesting suggestion is to attach a micropipet to a suction pump to get very localized vacuuming action. She also recommends always working in a fume hood and disinfecting any waste with a 70% solution of ethanol before disposal. She comments on the difficulty of removing stains caused by fungi and suggests trying a variety of solvents and/or bleaches appropriate to the object. The author concludes that the most important aspect is environment and regular monitoring of the collection to insure fungi cannot grow.
  • Szczepanowska, H. and C. M. Lovett Jr. 1992. A study of the removal and prevention of fungal stains on paper. Journal of the American Institute for Conservation 31 (2): 147-160.
    • This in depth and informative study examined the composition and removal of staining caused by pigments deposited from specific types of fungi often found on paper objects. Staining was induced on test samples that were treated locally and overall with dimethyl sulfoxide, 1,4-dioxane, N, N-dimethylformamide, triethylamine, pyridine, and 1,4 butanediol diglycidyl ether. For any of these treatments to be successful a 24 hour immersion was necessary, and the success of the treatment was dependent on the specific combination solvent and species of fungi. The study also looked at pH in relation to the production of pigment by fungi and found significantly greater pigmentation of the same mold species on paper samples with a pH of 5 rather than those with a pH of 8. They also found that temperatures of 4 ºC were successful at arresting growth and, depending on the species, the most intense growth occurred around 25 to 37 ºC. The four species of fungi in this study also showed more intense staining when exposed to light for 8 to 16 hours a day.
  • Szczepanowska, H. and W. R. Moomaw. 1994. Laser stain removal of fungus-induced stains from paper. Journal of the American Institute for Conservation 33 (1): 25-32.
    • This article presents the results of an experiment conducted to test the efficacy and safety of laser removal of fungal stains on paper. The authors used samples with induced staining as well as a 19th century Flemish etching for their experiments. Samples and controls were examined with stereomicroscopes and a scanning electron microscope. They used a YAG laser at 532nm to remove the fungal stains. They found that when used at an appropriate power it did not damage the paper and was successful on certain species of mold. The degree of success varied greatly with the species of mold, in some cases it removed the mycelium and the staining, in some cases one or the other, and in others there was no change. Lasers can cause instantaneous, irreversible blindness, and protective goggles must be worn.
  • Trentelman, K., W. R. Moomaw, and H. M. Szczepanowska. 1994. Letters to the editor: laser stain removal. Journal of the American Institute for Conservation 33 (3): 324-327.
    • This letter to the editor questions some of the methods and assumptions of the previous paper. The authors respond to the criticisms clarifying some points, and agreeing that more work needs to be done investigating the use of lasers for stain removal on paper objects.
  • Valentin, N. 1986. Biodeterioration of library materials disinfection methods and new alternatives. The Paper Conservator, 10: 40-45.
    • This paper looks at the long term effects of disinfection and conservation on paper, parchment, and microfilm in respect to susceptibility to fungal growth. From the samples of microfilm they found that a polyester base was more resistant to fungi than a cellulose acetate base. Disinfection using a spray or sublimed materials only worked to sterilize the surface of the samples. Also, if was found that objects which had previously been treated with ethylene oxide developed mold faster than objects that had not when each was placed in a warm humid environment. The author found that papers treated with barium hydroxide and calcium hydroxide were the most resistant to microbes. Gamma radiation was tested and found to prematurely age the substrate.

Studies of Mold on Photographic Materials

  • Caldararo, N and C. Griggs. 2001. Preliminary report on the conservation of slides with special reference to the removal of mold. Topics in Photographic Preservation 9: 97-102.
    • This study focused on finding a method to effectively remove mold hyphae without causing damage to the gelatin emulsion of 35 mm slides. Traditional solvent and mechanical methods of cleaning did not provide desirable results. A methodology was developed focusing on the properties of the cell walls of fungi, which are composed of chitin. Chitin is a polymer made up of repeating glucosamine units. Experiments with enzymes and NaCl to breakdown the chitin had only minimal success. The method the authors found that had the best results was to freeze the slides uncovered. When they were removed from the freezer a thin film of condensation formed on the slide, when this was wiped off with a swab. Most of the mold was removed and the emulsion was unaffected. The results were not totally predicable and often needed to be followed up with cleaning with 1:1 mineral spirits and water with 1% NaOH or Chitinase. The exact properties that allow for the success of the freeze cleaning are not fully understood.
  • Lavédrine, B. 2003. A guide to the preventive conservation of photograph collections. Los Angeles: Getty Publications. 132-142.
    • This article provides a good overview of what mold is and how to detect and sample it. The author also writes briefly about fumigation for effected storage areas. He recommends quarternary ammonium products, such as zinc Hyamine 1622 for disinfecting silver gelatin photographs and fluorosilicate for silver gelatin or color photographs. However, to be effective, the objects must be immersed and often the binder is too compromised to do so. Treatment with ethylene oxide fumigation is discussed as it is still used in France.
  • Lourenço, Miguel J. L.; Sampaio, José Paulo.2007. Microbial deterioration of gelatine emulsion photographs: a case study. Topics in photographic preservation Volume 12. 19-34.
    • Microbial deterioration is a common problem in photographic collections, and has been considered a major cause of deterioration. However, few studies have been carried out on this topic. Indeed, most of the literature is concerned with biodeterioration of archival documents in general, and this includes both micro and microorganisms. The environmental factors that promote this type of deterioration are well known and most of the published information is about prevention and control. There have been no detailed studies on the interactions between microorganisms, environment and the composition of photographic material. This study is focused on microbial deterioration of gelatine emulsion photographs, especially related to fungi. It was part of a global study of three collections in Lisbon, Portugal. The first part is a quantitative study on the microbial contamination of the Horácio Novais collection. The second is about induced contamination experiments of gelatine emulsion photographs. At the end these data will be analyzed taking into account the hypothesis that color materials are more susceptible to microbial deterioration than black and white ones. This hypothesis is based on the observations of several professionals working with photograph collections who report that, at least in plastic base supports (negatives and slides), color materials are frequently more contaminated than the black and white ones.
  • Zyska, B.J.; Cieplik, Z.T.; Wojcik, A.R.; and Kozlowska, R. 1988. Microbial deterioration of historic glass plate negatives.” In book. Biodeterioration 7: Selected papers presented at the Seventh International Biodeterioration Symposium, Cambridge, UK, 6-11 September 1987, ed D. R. Houghton, D. R. et. al. New York: Elsevier Applied Science Publishers Ltd. 428-435.
    • This study identified 13 species of mold growing on a selection of 5,414 glass plate negatives from The Krieger collection in the Historical Museum of the City of Cracow. The collection includes plates with collodion and gelatin emulsions. In general, varnish layers were the most susceptible.

Studies of Mold on Paintings and Textiles

  • Inoue, M and M. Koyano. 1991. Fungal contamination of oil paintings in Japan. Biodeterioration of cultural property. Koestler, R.J. ed. Elsevier: London: 23-35.
    • The high temperature and humidity common in Japan make it an ideal climate for fungal growth. The authors identified over 100 fungal species from 40 different Japanes oil paintings. In this article the authors discuss the results of a study using the fungicide, Vinyzene, in a synthetic resin coating to protect paintings from fungal attack. After 6.5 years of natural aging they found the varnish to have provided protection from fungi and only 3 of the 180 samples exhibited slight color change, which the authors speculate is a pigment specific reaction.
  • Koestler, R. J., E. Parreira, E.D. Santoro, P. Noble. 1993. Visual effects of selected biocides on easel painting materials. Studies in Conservation 38 (4). 265-273.
    • This paper shares the results of tests of four biocides (Vikane, Lysol, BioMet, and nitrogen gas) on combinations of linen, rabbitskin glue, lead white oil ground and oil paints. Nitrogen gas was the only one that did not produce a change in color or surface character of the samples. The drawbacks to nitrogen gas are that exposure needs to be several weeks long and it is only fungistatic not fungicidal.
  • Larochette, Y. 2003. Mold and museum artifacts. Unpublished. Research project for a preventive minor at the Winterthur/University of Delaware Program in Art Conservation.
    • This graduate student paper is a great introduction to dealing with mold in heritage collections. She briefly discusses the biology of mold and how to identify it; common treatments (mechanical removal, wet cleaning with alcohol and water solutions, freezing, heat, light, microwave and gamma irradiation, pressure, anoxia, fungicides and fungistats); and health and safety precautions. The author also includes a helpful annotated bibliography.
  • Montegut, D., N. Indictor, and R. J. Koestler. 1991. Fungal deterioration of cellulosic textiles: a review. Biodeterioration of cultural property. Koestler, R.J. ed. Elsevier: London: 209-226.
    • This paper provides a brief literature review of publications from 1940 to 1990 dealing with the fungal deterioration of cellulosic textiles. It is broken down into sections dealing with the “mechanism of attack”, “chemical protectants”, and “environmental control”.
  • Peltola, J., M. S. Salkinoja-Salonen, and S. Hornytzkyj. 2003. Biodeterioration of miniature paintings from the 18th and 19th centuries. In Molecular Biology and Cultural Heritage, ed. C. Saiz-Jimenez. The Netherlands: Swets & Zeitlinger. 79-84.
    • This article describes the examination of 150 painted miniatures on ivory or papier-mâché using stereomicroscopy and SEM. The authors discovered only certain pigments had mold growth, the earth colors and carmin, most other pigments used seemed to be resistant to the mold.


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