PMG Mold Remediation

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Date initiated September 2009
Contributors Chloé Lucas (Page Compiler), Cecilia Salgado, Susana Hoyos, Vanessa Castillo, Luisa Casella, Amanda Maloney, Stephanie Watkins



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What is mold?[edit | edit source]

Diagram showing the life cycle of a mold from the Aspergillus genus.
Life cycle of a mold from the Aspergillus genus

Several types of microorganisms can grow on photographic materials, the most common ones are bacterias and mold. Mold is a common term referring to filamentous fungal species from the Fungi Kingdom.


Life cycle of mold[edit | edit source]

Mold is present everywhere in the air in the form of mold fragments and reproductive cells, called spores. Fungi are heterotrophic organisms, which means that they cannot produce their own source of carbon to grow, it has to come from their environment. As a result, mold spores need to settle on an external source of carbon, which is called substrate, to grow. In favourable conditions, the spores then germinate and grow forming cylindrical branching filaments, called hyphaes. Once mature, the fungi can produce new spores that will contaminate other substrates.

For more information about mold biology, please refer to the section 1.2 of the BPG Mold page.


External factors influencing mold growth[edit | edit source]

Each fungal species has optimal environmental conditions in which they will grow best. However, they can still grow under less favorable conditions, the growth will be slower. Favorable conditions vary from species to species.

Several factors in the environment influence mould growth:

  • Water: Relative humidity in the environment around the photograph has an influence on fungal growth because it influences the moisture content of the substrate on which it grows. The ideal relative humidity for fungal growth is between 65% and 70%, but growth can easily happen at lower (55%) or higher relative humidities.
  • Nutrients: Photographic materials, such as cellulose (primary support) and proteins (image binder), serve as a source of carbon for mold growth.
  • Temperature: Each species has a minimum, maximum and optimal temperature for growth. The most suitable temperature is between 23.8ºC and 28.7ºC; however, some species can grow at lower (2ºC) or higher (40ºC) temperatures.
  • Light: The amount of light required for mold growth depends on species.
  • Oxygen: Fungi are strict aerobic microorganisms; oxygen is indispensable to their growth.


For more information about external factors influencing mold growth, please refer to section 1.6 of the BPG Mold page.

Effects of mold on photographic materials[edit | edit source]

Damage caused by mold[edit | edit source]

Mold damage may not always be visible to the eye, the fungal colony needs to be of a certain size and extent to start being visible.

Structural damages:

  • Change in mechanical strength.
  • Change in porosity.
  • Increased wettability.
  • Pitting of surfaces.
  • Friability.
  • Partial or total loss of binder, primary support.


Aesthetic damages:

  • Stains.
  • Change in gloss (from surface pitting).
  • Change in color.

Degradation mechanisms[edit | edit source]

During fungal growth, hyphaes adhere to their substrate and can generate micro-fissures into the constituent materials. Fungi secrete metabolic products which can react chemically with the materials and fragilize them through oxidation or enzymatic hydrolysis reactions.

Oxidation of proteins[edit | edit source]

Various fungal metabolic mechanisms, such as cellular respiration, can produce reactive oxygen species (ROS), [1] [2] which are highly reactive chemicals formed from dioxygen (O2).

ROS are rejected in the substrate and oxidize proteins, until full denaturation of the protein, which is the breakage of the alpha helix into a non-organised coil.[1] The breakage of the amino-acid chains increases the availability of amines and acids for reaction with water, resulting in an increased sensitivity to water of the protein.[3]

Some amino acids present in gelatin, methionine and tyrosine, are particularly sensitive to ROS (Barouki, 2006) and the secretion of ROS into the gelatin substrate results in its oxidation.[2]

Enzymatic hydrolysis[edit | edit source]

Fungal species can readily use simple sugars and amino acids to grow. In the presence of peptides or more complex sugars, such as cellulose, the fungi will need to produce enzymes specific to the materials, such as cellulase (for cellulose), protease (for proteins) or gelatinase (for gelatin), in order to break it down and use it as a carbon source.[4] Because simple sugars and amino acids are easier to assimilate, mould will be more likely to grow on an already broken down material, from previous water or fungal damage.[5]

Production of pigments[edit | edit source]

During growth, fungi can produce pigments, which can be located in the hyphaes, in the spores or secreted into the substrate. The production of pigments is species-dependent and is influenced by various factors such as the availability of nutrients, environmental factors or the presence of metal in the substrate. The formation of pigment can also result from the interaction between component materials and metabolic products.[4]

Intrinsic factors influencing mold growth[edit | edit source]

Presence of silver[edit | edit source]

The presence of silver as an image forming material has an impact on fungal growth. It was reported that low-density image areas, with lower amounts of silver, are more prone to fungal growth;[6] and that silver can completely inhibit fungal growth.[7] It was also noted that fungal growth on silver images can modify the localization of the silver within the binder, which accumulates on the surface of the fungal cell wall.[8]

Characteristics of gelatin emulsions[edit | edit source]

Tanning:

Tanning of emulsion during manufacturing or processing (fixing bath containing tanning agents) modifies its water content.[5]  Tanning, usually with chrome alum or formaldehyde,[9] results in reticulation of the gelatin peptide chains, thus preventing water molecules from linking with the chains, and lowering its water sensitivity.[3] Consequently, a tanned gelatin emulsion will have a water content between 3% and 9%, compared to a non-tanned gelatin emulsion whose water content is between 11% and 14%.[5] Fungi prefer their substrate to have a water content between 8% and 10%, so they are more likely to attack a non-tanned gelatin emulsion.[4]

Observations made by various authors sometimes contradict this information. Indeed, Abrusci et al. did not notice a difference in fungal development between tanned and non-tanned samples.[7] On the other hand, Dalev et al. showed that the more an emulsion is tanned, the slower the enzymatic hydrolysis will be, with solutilisation time of gelatin solution by protease enzymes increasing with the degree of reticulation.[10] Similarly, Lourenco and Sampaio noticed that early silver gelatin prints were more easily deteriorated by fungi, which could be explained by a lower degree of tanning.[6]

Amorphous and crystal phases:

The structure of gelatin consists of amorphous phase (coil) and crystal phase (triple helix). A gelatin emulsion with more crystalline areas will be more resistant to fungal attack, as the gelatin chains are organized into triple helix and less accessible to react with external molecules.[9]


Gel and solid phases:

Gelatin is a hygroscopic colloid, whose water content depends on the environmental temperature and relative humidity. The water content of gelatin influences its physical property, and two phases can be distinguished: a solid phase, under the glass-transition temperature, and a gel phase, above the glass-transition temperature.[11] Water in gelatin is not easily accessible to fungi when the gelatin is in a solid phase, it is more vulnerable to fungal growth when it is in a gel phase. The gelatin gel phase can be reached during thermo-hygrometric variations: when the temperature and relative humidity increase, the water content of the emulsion augments as well, it can go over the glass-transition temperature. This gel phase can also be attained when there is condensation on the surface of the emulsion.[5]

Health and safety[edit | edit source]

Health risks associated with mold[edit | edit source]

Contact with mold can cause different types of reactions to human health:

  • Allergic and hypersensitivity reactions: All mold species can induce allergic and hypersensitivity reactions as they are caused by the spores, mold fragments, biofilms and metabolic products secreted during mold growth. As the allergic and hypersensitivity reactions are caused by the presence of mold spores, fragments and biofilms, whether they are active or not, killing the mold does not eliminate the health hazard. The metabolic products are microbial volatile organic compounds (MVOCs), which are responsible for the moldy smell. Furthermore, MVOCs can be absorbed by porous substrates and be slowly released over time, the moldy smell can then indicate present or past mold growth.
  • Irritant and toxic reactions: Irritant and toxic reactions (respiratory, immune or neurologic effects) are less common as they are caused by mycotoxins secreted by some mold species, usually as a response to a stressful growth environment.
  • Infections: Mostly for people with severely compromised immune systems.


Sensitivity to mold varies from person to person, people with asthma or chronic conditions are more at risk. Moreover, the sensitivity increases with chronic exposure and permanent sensitization can occur over time. As a result there is no “safe” limit for mold levels, it is thus crucial to use protective equipment when working on contaminated photographs.

Protective equipment[edit | edit source]

Workspace[edit | edit source]

It is recommended to work in a space separate from non-contaminated materials and to isolate moldy materials to avoid cross-contamination.

The following workspaces are recommended for mold remediation treatments, depending on resources available, extent of contamination and size of photographs to be treated:

  • Biosafety cabinet (with High Efficiency Particulate Absorbing (HEPA) filters).
  • Fume hood.
  • Indoor. In a space with no air exchange with the rest of the building. Air vents can be sealed with plastic sheets and tape.
  • Outside. Under cover from the sun and far from building air intake.

Personal Protective equipment (PPE)[edit | edit source]

The mold exposure pathways into the human body are by inhalation, by ingestion, and by skin contact. It is necessary to protect your airways (nose and mouth), eyes and skin.


Airways protection:

  • Disposable respirator, half-face respirator, full-face respirator or powered air purification respiratory systems (PAPRs).
  • Particulate filters (N series), N100 (HEPA) is recommended.
  • Organic vapour filters can be added to the particulate filter, when there is a mouldy smell (presence of MVOCs).
  • /!\ Caution /!\ Filters have a limited lifetime, between 1 week and 1 month, depending on the model, frequency of use, air contamination and care.


Eyes protection:

  • Goggles


Skin protection:

  • Disposable gloves (PVC or nitrile)
  • Protective clothing if there is a significant amount of mould. Disposable (high contamination) or reusable (medium or low contamination).
  • Wash hands with soap and water after working on contaminated materials.


The type and extent of protection recommended varies depending on the size of the contamination. The Canadian Conservation Institute proposes a “Recommended Personal Protective Equipment” table to help determine which PPE to use, based on extent of contamination.


Should I use reusable or disposable PPE?

Reusable:

  • Must not be worn outside of a contaminated area to avoid cross-contamination.
  • Needs to be cleaned and disinfected after each use.
  • Can be shared only when they are properly cleaned and disinfected.


Disposable:

  • All disposable equipment is strictly personal and must not be shared.
  • Gloves and protective clothing can be reused until they are damaged and do not fulfill their safety purpose anymore. If reused, they must be cleaned before and after every use (before removing them):
  • Gloves: with soap and water, as a regular hand washing process.
  • Protective clothing: carefully vacuumed.
  • Discard in a sealed thick plastic bag in a regular garbage container. /!\ Caution /!\ Legislation may differ depending on location, consult local information sources.

Purpose of mold remediation for photographic materials[edit | edit source]

Factors to consider[edit | edit source]

Mold remediation treatments[edit | edit source]

References[edit | edit source]

  1. 1.0 1.1 Barouki R. 2006. “Stress oxydant et vieillissement”. Médecine/Sciences, 22, pp. 266-272.
  2. 2.0 2.1 Abrusci C., Marquina D., Santos A., Del Amo A., Catalina F. 2007. “A chemiluminescence study on the degradation of gelatin. Biodegradation by bacteria and fungi isolated from cinematographic films”. Journal of Photochemistry and Photobiology. A: Chemistry, 185, pp. 188-197.
  3. 3.0 3.1 Furic G. 2002. Les hospices civils de Lyon à l’exposition internationale urbaine de 1914. Étude et restauration de trois photographies sur papier au gélatino-bromure d’argent montées sur toile tendue sur châssis. Étude de la dégradation des papiers au gélatino-bromure d’argent à l’humidité. Mémoire de fin d’étude. Saint-Denis La Plaine: Institut national du patrimoine.
  4. 4.0 4.1 4.2 Florian, M-L. 2002. Fungal facts: solving fungal problems in heritage collections. London: Archetype Publications Ltd.
  5. 5.0 5.1 5.2 5.3 Florian M.-L. 2003. “Water, heritage photographic material and fungi”, Topics in Photographic Preservation, 10, pp. 60-73.
  6. 6.0 6.1 Lourenço M. J. L., Sampaio J. P. 2007. “Microbial deterioration of gelatin emulsion photographs: a case study”. Topics in Photographic Preservation, 12, pp. 19-34.
  7. 7.0 7.1 Abrusci C., Marquina D., Del Amo A., Catalina F. 2003. “Biodegradation of cinematographic gelatin emulsion by bacteria and filamentous fungi using indirect impedance technique”. International Biodeterioration & Biodegradation, 60, pp. 137-143.
  8. Schlocchi M. C., Daminao E., Matè D., Colaizzi P., Pinzari F. 2013. “Fungal biosorption of silver particles on 20th century photographic documents”. International Biodeterioration & Biodegradation, 84, pp. 367-371.
  9. 9.0 9.1 Glafkidès P. 1976. Chimie et physique photographiques. Paris : Photo-cinéma / Paul Montel.
  10. Dalev P., Vassileva E., Mark J E., Fakirov S. 1998. “Enzymatic degradation of formaldehyde crosslinked gelatin”. Biotechnology techniques, 12, 12, pp. 889-892.
  11. Adelstein P. Z., Bigourdan J.-L., Reilly J. M. 1997. “Moisture relationships of photographic films”, Journal of the American Institute for Conservation, 36, 3, pp. 193-206.

Further reading[edit | edit source]

General information[edit | edit source]

  • 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[edit | edit source]

  • 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[edit | edit source]

  • 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.

Mold remediation treatments[edit | edit source]

  • 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.

Case studies[edit | edit source]

  • 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.


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