A chart entitled "Framework for Preservation of Museum Collections" has been developed by the Environment and Deterioration Research Division of CCI. It is intended to assist conservators, collection managers, and other museum professionals in assessing the threats to their collections.

The chart was initially developed by Stefan Michalski to help individuals assess the dangers to their collections objectively. Since the 1960s, conservators have been concerned about the museum environment, in particular about relative humidity, light levels, pollution, and temperature. Pests are also a concern, but often are considered separately from environmental factors. However, none of these factors had traditionally been grouped with other serious threats to a collection, such as breakage, theft, fire, or water damage. This incongruity became apparent when CCI staff were carrying out "environmental surveys" of museums; there were some museums that had purchased hygrothermographs when they had no smoke or fire detectors, or that were concerned about ultraviolet light when they had inadequate locks on the museum doors.

The "Framework for Preservation of Museum Collections" consists of a 9 row by 7 column matrix. Along the left-hand side of the chart, various threats to museum collections are grouped into nine agents of deterioration: direct physical forces; thieves, vandals, and displacers; fire; water; pests; contaminants; radiation; incorrect temperature; and incorrect relative humidity. The type of museum object that is vulnerable to each agent is identified, along with the type of damage that can occur. The columns outline methods of control that can be carried out at each of three different levels or scales: the building (architectural or engineering elements), portable fittings (items or modifications that are generally purchased on an operating budget), and procedures (actions that can be carried out by museum staff). Control at the building or portable fittings level is further broken down into actions that are suitable for storage, display, or transit situations. Each cell of the matrix lists stages for controlling an agent of deterioration under five general headings: avoid, block, detect, respond, and recover/treat.

In this article, I will restrict my discussion to the principal agents of deterioration that are outlined in the Framework, and will discuss some examples of how the Framework might be used.

Agents of Deterioration

The nine agents of deterioration group together various active agents that threaten museum collections. The relative order of importance of these agents was generally determined by the severity of damage that each inflicts on an object and by the overall likelihood of this damage occurring. The actual order of importance of the agents may differ for a given institution or for a particular situation.

Direct physical forces can be either sudden and catastrophic or long-term and gradual. Sudden damage usually results from a shock to the artifact while it is being handled or moved, during collapse of shelving or supports, or as a result of earthquakes or war. Long-term exposure to some force may result in the deformation of an object, and may be due to inadequate support in display or storage or to artifacts having been stacked. Vibration can also cause damage to artifacts in the short term or the long term, depending on the circumstances. The most common damages in this category result from improper handling procedures, and the type of damage varies from complete loss of the artifact to minor damage that can be repaired. Most museum artifacts are vulnerable to this type of direct physical force.

Most of the risks in the category of thieves, vandals, and displacers are traditionally covered by museum security services in large institutions. Thieves obviously are a great concern because museum objects have a high value, their location and existence are well known, and if an object is stolen the loss is total. Vandals tend to attack high-profile or noticeable items, and often inflict severe damage. The agent "displacers" addresses the problem of artifacts that are misplaced within the museum; this is usually done inadvertently by staff members in storage areas. If an artifact or specimen has been misplaced and cannot be found, the effect is the same as a theft.

Fire obviously poses a threat to all museum collections, although organic artifacts are particularly vulnerable. In addition, smoke from fires poses a particular threat, especially to porous specimens. Although fires are infrequent, they result in massive loss and extensive damage.

Water is a major threat to museum collections because of leaking roofs, skylights, or water pipes. Flooding or fire suppression equipment may also cause water damage. Porous organic materials, metals, and composite materials (i.e., materials that are layered or joined) are particularly susceptible to water damage. In addition, many artifacts have some component that is wholly or partially soluble in water.

There is an obvious relationship between the risks from the threat of fire and the risks of water damage from having a sprinkler fire suppression system. Although the risk of a sprinkler malfunction may be greater than that of a fire, the damage caused by a fire is much more extensive and devastating to the collection than that caused by water. The Fire Protection Advisor at Heritage Services, CCI, who has inspected hundreds of museums and has seen the results of a number of museum fires, strongly recommends installing sprinkler systems.

The agent of pests includes attack by insects, vermin, or mould. The threat here is primarily to organic materials, which can be damaged either because they are a food source to the pest or because they represent a barrier that the pest wants to cross. Damage can be extensive if pests become established (i.e., begin to live, eat, excrete, and die) in the museum collection. Problems with mould and microbes are related to problems with relative humidity.

Contaminants is the term used to describe chemical agents from the museum environment that can cause some alteration of museum objects. Contaminants can be in the form of gases, liquids, or solids. Gaseous contaminants are frequently considered to be pollutants, although the source of the gas may be external industrial and vehicle emissions (e.g., sulphur dioxide or nitrogen dioxide), gases emitted by materials within the museum (e.g., vapours given off by wood, coatings, or other artifacts), or oxygen present in the atmosphere. Liquids that might contaminate museum objects include plasticizers migrating from plastics, and grease deposited by improper handling. The most common solid contaminants are salt (either airborne or from handling) and dust. Contaminants can result in complete destruction of an artifact over a prolonged period of time, but more often result in some disfigurement of the artifact.

Radiation includes ultraviolet and visible light. Ultraviolet radiation can cause disintegration and discolouration of the outer layers of organic objects, and visible light can cause fading (or, less often, darkening) of the outer layers of coloured components in artifacts. Ultraviolet light is not necessary for humans to view museum objects, and so should be avoided or eliminated in museum display and storage areas. Some visible light is necessary to allow visitors to see objects on display, but this must be balanced against the stability of the colorants in the objects. Fugitive colorants will change noticeably after just a few years of display, even if they are displayed at low light levels (50 lux). Light damage will not cause complete physical destruction of an artifact, but can affect the relevance of or the interest in an object and can reduce its value considerably. Discolouration caused by light damage cannot be repaired or reversed.

Temperature is a measure of a physical property and by itself cannot directly cause damage to museum objects. However, damage to museum collections does result from incorrect temperatures, which can be broken down into three different types: temperatures that are too high, too low, or fluctuating. High temperature can result in accelerated degradation rates of chemically unstable components, low temperature can cause embrittlement of some materials, and fluctuating temperatures can cause materials to fracture or delaminate. Although temperature levels within museums are usually dictated by human comfort levels, low-temperature storage areas are used for certain unstable artifacts such as colour photographs. Temperature can be very important in determining the useful life of chemically unstable artifacts such as photographic films and acidic paper.

Incorrect relative humidity can be broken down into four subgroups: damp (over 75%), above or below a critical value, above 0%, and fluctuations. Mould growth can occur when the relative humidity is over about 75%, and certain minerals or contaminated metals deteriorate above or below critical relative humidity values. Some chemical deterioration reactions slow as the relative humidity is reduced, and stop when the relative humidity drops to 0%. Relative humidity fluctuations cause swelling or shrinkage of organic components, which can result in fracture, crushing, or delamination of organic components. Although incorrect relative humidity can result in considerable damage to vulnerable artifacts, in most cases it does not lead to complete destruction of artifacts.

We have found the "Framework for Preservation of Museum Collections" to be an extremely useful tool in assessing the risks posed by particular situations. The Framework's usefulness is not only due to its comprehensive nature, but also because it identifies potential areas of risk rather than directly identifying deficiencies.

Example 1

Consider a hypothetical situation where a large gallery receives a loan request from a small community museum nearby for a series of graphite pencil sketches on white rag paper that are of particular historical significance to the district. To make the situation more interesting, suppose that the director of the large gallery would like to agree to the loan but the curator involved has grave concerns about the risks to the works of art, and that the conservator is receiving subtle pressure from both sides. One method of resolving this predicament would be for the conservator to meet with the responsible person from the requesting institution and to use the Framework to describe the range of potential dangers to the works of art, identify the agents of deterioration that are pertinent in this situation, and then find ways of reducing the risks.

If the large institution is concerned about direct physical damage occurring during transit and handling, it may be possible to arrange for staff from the large museum to deliver and install the works. Security will clearly be a major concern, so arrangements must be made for securing the museum building, for exhibiting the works (i.e., display case, alarms), and for the presence of security personnel. Concerns about fire suppression, leaky roofs, and pest control will have to be discussed. Because the works in question are on untinted rag paper and are in stable condition, light levels are not a major concern within the range of 50 lux to 300 lux, as long as the ultraviolet component is filtered out. A discussion of the temperature and relative humidity within the borrowing museum shows that the temperature control is moderately good (between 18^oC and 24^oC), but that the relative humidity can only be maintained at 25%. Because the works are properly hinged and matted and because no thick paints are present, this will not pose any serious risk. Therefore, it may turn out that the only major risk that needs to be addressed is security. Further discussion between the borrowing institution, the reluctant curator, the director, the conservator, and possibly a security expert may be necessary to determine whether or not this risk can be safely controlled. No matter what the outcome, at least the decision will have been made on a factual, rational basis that can be clearly understood by all involved.

Example 2

Museums are under increasing pressure to allow more public access to their collections. The Framework may be useful in addressing the risks involved with this access.

Let us consider another hypothetical situation where a curator is planning to include a number of pieces of 19th- and 20th-century furniture in a public session to let members of the public interact more closely with the collection. In addition to security and transit concerns, there may be an increased risk of artifacts being broken and contaminated (i.e., soiled) due to improper or unauthorized handling. Also, in this case, it is possible that a number of the pieces are quite vulnerable to relative humidity fluctuations, in which case humidity control is essential. All of these considerations may result in a decision to have the public session take place in an available gallery within the museum rather than in some outside location.

Conclusion

The nine agents of deterioration outlined on the "Framework for Preservation of Museum Collections" make up a comprehensive list of the various situations that can threaten museum, gallery, or archival collections. CCI staff members have found the Framework to be an extremely useful tool for identifying risks to museum collections and for suggesting appropriate methods of control. For a copy of the "Framework for Preservation of Museum Collections" poster, visit our online Bookstore.