Agents of Deterioration
Robert Waller of the Canadian Museum of Nature and Stefan Michalski of the Canadian Conservation Institute have been the primary proponents of applying risk management strategies to museum collections. This approach has found wide acceptance in the preservation community as a tool for helping institutions assess risks to collections and find an appropriate balance between the requirements for use (i.e. research, display and education) and preservation.
Examining whether a risk is likely or unlikely to occur and whether it would result in minor or major loss aids in setting preservation priorities. Risk is broken down according to ten agents of deterioration that pose threats to collections.
Damage from exposure to visible light, and ultraviolet and infrared radiation is cumulative and irreversible. It is a function of intensity over time, and therefore even low intensity light can make an impact if objects are exposed over a long period time. Common impacts are fading or discoloration, as well as unseen chemical changes that cause embrittlement in organic materials.
Examples of Damage
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- Preventive Care Strategies for managing Light, Ultraviolet, and Infrared
- CCI Agents of Deterioration: Light, Ultraviolet, and Infrared
Temperature is a measure of heat energy, and damage may occur when the temperature is either too high or too low. High temperatures increase the rate of chemical reactions, soften materials, and desiccate organic materials. Low temperatures can cause hazing and cracking. Temperature directly affects relative humidity, and consequently a fluctuating temperature leads to a fluctuating relative humidity.
Examples of Damage
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- Preventive Care Strategies for managing Temperature
- CCI Agents of Deterioration: Incorrect Temperature
Relative humidity (RH) is a ratio (expressed in percent) between the mass of water vapor in a fixed volume of air (the absolute humidity) and the maximum mass of water vapor that a fixed volume of air could hold (without condensation) at the current temperature. All organic materials and some inorganic materials absorb and release water depending on the relative humidity of surrounding air. High RH can cause mold growth and corrosion; low RH can cause shrinking and cracking in organic materials.
Examples of Damage
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- Preventive Care Strategies for managing Relative Humidity
- CCI Agents of Deterioration: Incorrect Relative Humidity
Pollutants are derived from contaminants produced both outside and inside of collecting institutions. Particulate and gaseous contaminants can be airborne, transferred by contact, or contained (inherent) within objects themselves. Common examples of pollution include dirt, soot, volatile components from plastics and wood, and residual pesticides.
Examples of Damage
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- Preventive Care Strategies for managing Pollutants
- CCI Agents of Deterioration: Pollutants
Museum pests are animals and microorganisms that are attracted to and capable of consuming or otherwise damaging museum collections and/or their storage and exhibit materials. Most prominent are invertebrate pests, such as moths and carpet beetles, but vertebrates such as rodents, and microorganisms like mold, can also cause catastrophic damage.
Examples of Damage
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- Preventive Care Strategies for managing Pests
- CCI Agents of Deterioration: Pests
Physical forces act on museum collections in swift and disastrous ways, such as human error in dropping an object or a natural disaster that collapses a building, or in prolonged repeated exposure, such as daily touching by the public or vibrations from nearby trains. Deterioration results in breaks, loss, and loose components.
Examples of Damage
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Fire can quickly lead to complete loss of a collection. Even if objects are not consumed by the fire itself, damage can occur from smoke soot deposits, as well as water damage from extinguishing.
Examples of Damage
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Exposure to water alone does not often cause extreme or instant damage, in fact many conservation treatments involve water. However, when materials are exposed to large quantities of water at once, such as a pipe burst or flood, it can cause saturation and fragility, soiling, and inhibit mold growth.
Examples of Damage
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Theft can include planned robbery of important or valuable pieces in collections, opportunistic theft by visitors, embezzlement by staff, and vandalism.
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Custodial neglect occurs when preventive and interventive conservation measures are not taken to protect a collection, such as not correcting improper environmental conditions and using non-archival storage or exhibition materials. Custodial neglect also occurs when objects are disassociated from their records.
Example of Damage
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Nine of these risks are physical (physical forces, fire, water, criminals, pests, pollutants, light, incorrect temperature, and incorrect humidity) and the tenth is custodial neglect. This tenth agent is most dependent on issues relating to general collections management policies. Risk for all of these agents of deterioration can be controlled at many levels—from the site location, down through the building, room, cabinet, or object. It can also be controlled by implementation of proper policy and procedures.