ALL OBJECTS, sooner or later, begin to break down and deteriorate. Ten agents of deterioration, or primary threats to collection objects, have been identified as the causes of object loss in collections, and these should be the focus of long-term preventive care efforts.1 The ten agents of collection deterioration include:
Preventive care (also called preventive conservation) is one of the most useful tools registrars and collection managers have for ameliorating the effects of the agents of deterioration and working toward the goal of collection preservation. Although many professional organizations have definitions for preventive care, I will use the definition developed by our colleagues at the American Institute of Conservation (AIC):
The mitigation of deterioration and damage to cultural property through the formulation and implementation of policies and procedures for the following: appropriate environmental conditions; handling and maintenance procedures for storage, exhibition, packing, transport, and use; integrated pest management; emergency preparedness and response; and reformatting/duplication.2
Conservation is devoted to the preservation of cultural property through examination, documentation, treatment, and preventive care. Conservators are specially trained professionals within their specialization, but registrars and collection managers are often the ones who find themselves in charge of carrying out preventive conservation as part of their institution’s preservation program, and facilities and administrative staff can frequently be good allies in establishing and maintaining the proper physical, structural, and mechanical standards within the facility.
The quality of the storage environment has a significant long-term effect on the preservation of objects. The storage environment refers to both collection storage areas and objects on exhibit because exhibition is a form of storage. Generally, the most critical storage environment concerns are:
Taken together, these five factors establish the overall quality of the storage environment.
To create a good storage environment a holistic approach must be used that takes into account the needs of the objects (predominately based on the materials that compose them), the building mechanical systems (heating and cooling), and institutional resources and priorities.3
Variations in environmental standards can cause irreversible damage to collection objects; therefore, changes to the storage environment standards must be made with the utmost care and caution, taking into consideration not only the care of the collections but also concerns for borrowed objects, the physical structure of the institution, and current information about and standards for storage environments. If these elements are not considered, then the following kinds of damage can occur:
Temperature and relative humidity standards have undergone changes in recent years as research by the Image Permanence Institution5 (IPI), the Canadian Conservation Institute6 (CCI), and others has broadened our understanding of how materials react to changes in the storage environment. Traditionally, a universal standard of 70°F ± 5° and 50 percent relative humidity ±5 percent was encouraged for all collection storage. Although this standard was once a good rule of thumb, the emphasis now is on establishing set points for temperature and relative humidity that are based on the materials the collection objects are composed of and what the building heating and cooling systems can reasonably maintain with minimal fluctuations in a particular geographic area. Bear in mind that many external factors affect indoor temperature and relative humidity, including location and climate.
In general, conditions of lower temperatures and moderate relative humidity will extend the preservation of the collection by slowing chemical reactions and, thus, slowing the rate of chemical decay. However, temperature and relative humidity that are too low may cause some materials to contract and become brittle.7
Relative humidity is the amount of water vapor in a given quantity of air compared to the amount of water vapor that same quantity of air could hold if it was saturated, expressed as a percentage.8 Temperature and relative humidity are directly related; warm air can hold more moisture than cold air, which means that if a given quantity of air is heated, its relative humidity goes down, but if that same quantity of air is cooled, its relative humidity goes up.9 This is why fluctuations in temperature cause fluctuations in relative humidity, which is always a concern in collection storage. For example, if warm, moist air in collection storage is cooled sufficiently the moisture in the air will begin to condense on the surface of the objects in storage because the cool air cannot hold as much moisture as the warm air. Large fluctuations in relative humidity are often the chief culprit in collection damage:
Large fluctuations in relative humidity can be avoided by creating microenvironments inside object containers, storage cabinets, or exhibit cases, using good quality materials and adding a moisture absorber such as silica gel. For oversized museum objects, polyethylene sheeting can be draped over shelving or cabinets to create a buffer for fluctuations.11 Inside these microenvironments the relative humidity and temperature will remain more stable, which is safer for the objects they contain. Microenvironments are particularly useful when objects are moved long distances. Keeping objects in closed cabinets or exhibit cases with good seals will slow the air exchange rate so that the objects inside can adjust more slowly to fluctuations in temperature and relative humidity. The materials used to create microenvironments must be specially prepared before use.12
The staff at each facility need to establish a target set point or target value for temperature and relative humidity that the building’s mechanical system can maintain over time (in geographic locations with widely varying climate over the year, different summer and winter set points may be chosen).13 To determine an appropriate set point the following factors should be considered:
Storage environment experts agree that avoiding large fluctuations over a short period of time is the goal that staff must aim for, but this has to be accomplished with the resources that are available and by establishing set points that can be maintained. Most heating and cooling standards are meant for human comfort rather than long-term preservation so your set points may conflict with the concept of a sustainable green building; hence, the storage environment standards will likely not be the same as environmental standards throughout the museum (see chapter 6f, “Registrars and Sustainability”).
Several organizations have published models and worksheets to help museums establish appropriate set points, including CCI and the IPI (which sells an Environmental Monitoring Starter Kit). When establishing set points, it is important to think long term and consider daily, monthly, and annual environmental cycles.
Although light is required to view objects, too much light can cause irreversible harm to many materials.14 Like other forms of radiation, both the intensity and the time of exposure are critical factors for light (e.g., a short exposure to an intense radiation source can cause as much damage as a prolonged exposure to a less-intense source). Light is radiant energy that can be considered in three categories that affect objects:
Damage from exposure to the different types of radiation varies, but all radiation damage is cumulative and irreversible. Examples of light damage include:
Direct sunlight is the most damaging form of light because it includes visible, UV and IR radiation. Equipping windows with blinds, shutters, or curtains and avoiding skylights are the easiest ways to control daylight. UV blocking film, acrylic, or glass can reduce UV damage but not that from visible light.17
Artificial light sources must be selected with care. There are three basic types of artificial light sources commonly used in museums—incandescent, f luorescent, and LED. An incandescent lamp has a wire filament inside a glass bulb that is heated until it glows, producing light, but also heat. Many types of incandescent bulbs produce significant amounts of UV radiation (e.g., halogen lights). Fluorescent lamps contain mercury vapor inside a glass tube that has a phosphor coating. When a fluorescent light is turned on, the electric current excites the mercury vapor, which, in turn, causes the phosphor coating to glow, producing visible light and large amounts of UV radiation, but little IR radiation. LED lamps contain semiconductors called light emitting diodes (LEDs) that produce light when electricity is applied to them but do not produce significant amounts of UV or IR radiation. Which light source is best depends on the situation in which it is used. Advice on selecting light sources can be obtained from lighting experts or sources such as CCI.18 Permissible and appropriate light levels for objects in storage or on exhibit depend on a number of factors including the light sensitivity of the materials, ambient lighting in the room or gallery, how the object is stored or exhibited, etc. The traditional exposure standards for several decades was 50 lux for textiles, works on paper, water-colors, photographs, feathers, etc.; 150 lux for oil and acrylic paint surfaces, polychrome panels, and furniture, etc.; and 300 lux for stone and metal, primarily to avoid contrasting lighting. Light levels should be based on a risk management strategy that considers the fading and ease of visibility of the objects.
Visibility is an important factor to keep in mind when considering light levels because older visitors and many vision impaired visitors need more illumination than an average visitor. CCI recommends adjustments to light levels that will provide equal visibility of objects while still meeting long-term preservation goals.19
Once light levels are set, various tools can be used to test and calculate the rates of light deterioration. The International Standards Organization (ISO) Blue Wool Standard,20 developed in the 1920s, is based on the light sensitivity of a special blue dye over time and can be used to estimate the amount of light-fading. The CCI has an online light damage calculator that provides assistance in determining light levels.21
Damage caused by pests is a frequent issue in collection storage areas. Pests are often drawn to organic collection materials as well as storage and display materials. To prevent pest damage, institutions are encouraged to establish an integrated pest management (IPM) plan, which is an inclusive and holistic approach to prevent and deal with pests and pest infestations.22 The practice of IPM involves monitoring for pests by examining the building and using traps, sealing entrances to the building to prevent pests from entering, and keeping areas where collection objects are stored cool and dry, and maintaining good air circulation. When pests are found, nonchemical methods of eradication are pursued first to avoid the use of pesticides that can harm objects and humans (see chapter 6e, “Integrated Pest Management”).
The introduction of contaminants in collection storage areas can cause many forms of damage including disintegration, discoloration, and corrosion of objects. Natural oils and salts from your hands may not appear to cause immediate damage, but over time fingerprints will permanently mar various materials, especially metal surfaces, gilded surfaces, and photographs.23 For this reason, the use of gloves is generally encouraged. Some registrars and collection managers are promoting the idea of using clean, bare hands when handling certain types of objects because gloves reduce the sensitivity of touch, but these decisions must be carefully considered, weighing the potential of contamination by natural salts and oils against the potential damage from an insecure grip. If gloves are used, clean cotton or nonpowdered nitrile gloves are generally recommenced (however, do not use nitrile gloves when handling silver).24
Airborne pollutants can come from outside or inside the museum. Outdoor generated pollutants include pollen, dust, fibers, and soot, which are introduced into the museum environment through open windows and doors, unfiltered ventilation systems, or on people’s clothes or bodies.25 Other significant outdoor pollutants include sulfur dioxide, nitrogen dioxide, nitrogen oxide, ozone, and reduced sulfur gases such as hydrogen sulfide. Common indoor generated gases include acetic acid, formic acid, acetaldehyde, formaldehyde, hydrogen sulfide, carbonyl sulfide, and ozone. Many of these gases are produced by the off-gassing of paints, carpets, and cleaners.26 Of particular interest is ozone, an air pollutant that can be generated both outdoors and indoors and that can damage both organic and inorganic materials. Outdoor generated ozone is a component of smog; indoors, ozone is produced in large amounts by photocopiers and air purifiers.27
Pollutants should be minimized or eliminated by avoiding the source (when possible) and by the use of air filtration systems. Further protection can be provided by using neutral materials such as untreated cotton, polyethylene sheeting, and acid-free board, and by storing objects in sealed cabinets that have synthetic gaskets. Avoid placing collection objects where they are likely to come into direct contact with pollutants such as near copy machines.28 Store chemicals—including cleaning products, paints, and any other substance that might off-gas—in a secure area well away from collection objects.
Following appropriate handling procedures is important for ensuring the long-term preservation of collections because objects are at their most vulnerable when being handled (see CHAPTER 5B, “Object Handling”). Dents, scratches, cracks, and breaks may all result from physical forces during handling.29 Packing and shipping may also cause damage to collections, even under the watchful eye of collections staff (see CHAPTER 5N, “Packing and Crating”).
Establishing procedures to ensure object safety and guidelines for handling and moving objects and identifying materials and techniques for packing and shipping objects are all part of preventive care. Additional information can be found in chapter 6 of the National Park Service Museum Handbook for creating procedures for your institution.30
Work with facilities and administrative managers to ensure that the physical plant and mechanical systems will not cause harm to the collections.31 The CCI has a list of basic requirements that should be met by buildings and facilities that is an excellent guide for staff to use,32 including:
Mechanical systems should be energy efficient, and collection objects should not be stored near them. Attics, basements, and rooms with water pipes (other than sprinklers) or other features that could leak should not be used for collection storage. Rooms that have direct access to the outside environment should only be used for collection storage if windows and doors are properly sealed.
Housekeeping plans should cover all spaces containing collections and include the following:
A good housekeeping plan will prevent damage by controlling the amount of dust and grit in the collection and establishing a routine methodology for collections care and maintenance. CHAPTER 13 of the National Park Service Museum Handbook contains more information regarding how housekeeping plans can be created and implemented.33
Emergency preparedness and response is also an element of preventive care.34 Preventive care is defined as taking steps to prevent damage, and an emergency plan reduces the chance of damage when disaster strikes (see CHAPTER 6B, “Emergencies: Prepare, Respond, and Recover”). Practicing the emergency plan gives staff the opportunity to get to know the building better and is an excellent opportunity for facilities and frontline staff to learn about collections storage areas they might not usually access.
Recordkeeping is essential for a successful institutional preventive care program. Recordkeeping includes tracking temperature, relative humidity, and light levels; recording evidence of pests; identifying contaminants; maintaining housekeeping schedules; and organizing resources for emergencies; as well as information recorded in collection records and condition reports. All of this information is extremely useful for collections staff in combating deterioration of collection objects. Environmental records are important to identify trends and develop a long-term collection care plan based on preventive conservation, object-specific assessments, environmental and storage upgrades, and conservation management.35
Although preventive care may seem like a daunting task, by paying attention to the storage environment and how collections are stored and handled, deterioration of objects can be minimized in the future. •
1. Available at: https://www.canada.ca/en/conservation-institute/services/agents-deterioration.html.
2. Available at: https://www.culturalheritage.org/about-conservation/what-is-conservation/definitions.
3. G. Fisher, “Preventive care,” in R. A. Buck and J. A. Gilmore, eds., Museum Registrations Methods, 5th ed. (Washington, DC: American Association of Museums Press, 2010).
4. Fisher, “Preventive care.”
5. Available at: https://www.imagepermanenceinstitute.org/.
6. Available at: https://www.canada.ca/en/conservation-institute.html.
7. Image Permanence Institute, Sustainable Preservation Practices for Managing Storage Environments (Rochester, NY: Rochester Institute of Technology, 2011). Available at: http://ipisustainability.org/pdfs/sustainability_workbook_georgia.pdf.
8. Fisher, “Preventive care.”
9. David Grattan and Stefan Michalski, “General care and preventive conservation,” Canadian Conservations Institute. Available at: https://www.canada.ca/en/conservation-institute/services/preventive-conservation/environmental-guidelines-museums/general-care-preventive-conservation.html (accessed December 2, 2018).
10. James M. Reilly, “Fundamentals of the preservation environment,” presented April 26–27, 2010. Available at: http://www.ipisustainability.org/pdfs/western/Reilly_FundamentalsPreservationEnvironment.pdf.
11. National Park Service, “Creating a microclimate for oversized museum objects,” Conserve O Gram, no. 4/4 (July 1993). Available at: https://www.nps.gov/museum/publications/conserveogram/04-04.pdf.
12. T. J. Raphael, “Airtight, humidity stabilized display cases: The practical design and fabrication of sealed exhibit cases,” Objects Specialty Group Postprints 1 (1991): 78–87.
13. Stefan Michalski, “Agent of deterioration: Light, ultraviolet and infrared,” Canadian Conservations Institute. Available at: https://www.canada.ca/en/conservation-institute/services/agents-deterioration/light.html (accessed December 4, 2018).
14. Fisher, “Preventive care.”
15. Michalski, “Agent of deterioration.”
16. Fisher, “Preventive care.”
17. Fisher, “Preventive care.”
18. Available at: https://www.canada.ca/en/conservation-institute/services/agents-deterioration/light.html.
19. Available at: https://www.canada.ca/en/conservation-institute/services/agents-deterioration/light.html#l3.
20. Available at: http://cameo.mfa.org/wiki/Blue_Wool_Standard.
21. Available at: https://app.pch.gc.ca/application/cdl-ldc/description-about.app?lang=en.
22. Integrated Pest Management Working Group, MuseumPests.net. Available at: https://museumpests.net/ (accessed December 6, 2018).
23. Janet Mason, “Handling heritage objects,” Canadian Conservations Institute. Available at: https://www.canada.ca/en/conservation-institute/services/preventive-conservation/guidelines-collections/handling-heritage-objects.html (accessed December 5, 2018).
24. Robert L. Barclay, Carole Dignard, and Lyndsie Selwyn, “Caring for metal objects,” Canadian Conservations Institute. Available at: https://www.canada.ca/en/conservation-institute/services/preventive-conservation/guidelines-collections/metal-objects.html (accessed December 10, 2018).
25. Fisher, “Preventive care.”
26. Cecily M. Grzywacx, Tools for Conservation: Monitoring for Gaseous Pollutants in Museum Environments (Los Angeles: The Getty Conservation Institute, 2006).
27. Fisher, “Preventive care.”
28. E. D. Duyck, “Chapter 7, Museum Collection Storage,” in The Museum Handbook Part 1: Museum Collections, 14 (Washington, DC: National Park Service Museum Management Program, 2012). Available at: https://www.nps.gov/museum/publications/MHI/CHAP7.pdf
29. Mason, “Handling heritage objects.”
30. J. S. Johnson, “Chapter 6, Handling, Packing, and Shipping,” in The Museum Handbook Part 1: Museum Collections (Washington, DC: National Park Service Museum Management Program, 1999). Available at: https://www.nps.gov/museum/publications/MHI/CHAP6.pdf.
31. Fisher, “Preventive care.”
32. Stefan Michalski, “Basic requirements for preventive conservation,” Canadian Conservations Institute. Available at: https://www.canada.ca/fr/institut-conservation/services/conservation-preventive/lignes-directrices-collections/exigences-base-conservation-preventive.html (accessed December 11, 2018).
33. J. S. Johnson, “Chapter 13, Housekeeping,” in The Museum Handbook Part 1: Museum Collections (Washington, DC: National Park Service Museum Management Program, 1998). Available at: https://www.nps.gov/museum/publications/MHI/CHAP13.pdf.
34. J. Levin, “Preventive conservation,” Conservation Perspectives: The GCI Newsletter 7, no. 1 (1992). Available at: http://www.getty.edu/conservation/publications_resources/newsletters/7_1/preventive.html.
35. Fisher, “Preventive care.”