Agents of Deterioration
Protecting collections can be hard, especially when there are so many ways in which an object can deteriorate or become damaged.
It's crucial to remember that it is in the nature of all materials to deteriorate. But there are preventative actions that can be taken to slow the deterioration process.
This information is provided for informational purposes only. If you have items of historical or cultural value, a conservator should be contacted. You can locate a conservator near you with AIC's Expert Search tool.
Temperature & Relative Humidity
Temperature and relative humidity are a two-for-one agent. They often work hand-in-hand and cause damage to artifacts. Any extremes or large fluctuations should be prevented.
Temperature
High temperature can cause:
- Softening of meltable materials like waxes and resins
- Embrittlement and weakening of materials
- Faster desiccation (drying) causing loss of flexibility and cracking
- Composite objects may have different rates of expansion and contraction creating splits and cracks along the join lines
Low temperature causes materials to contract which can led to embrittlement, hazing and cracks.
Relative Humidity
Relative humidity refers to the amount of moisture in the air.
High relative humidity (above 60-65%) can accelerate chemical deterioration and promote mold growth. Low relative humidity (below 40%) can cause shrinking, warping, cracking, embrittlement and desiccation.
Large and frequent fluctuations in relative humidity can cause shrinkage, warping, splitting and general aging of organic materials.
Composite objects are at greater risk of damage caused by relative humidity because each material will react differently to any changes.
Pollutants
Pollutants can be generated inside and outside buildings. Many pollutants known to cause health problems in humans can also damage your collections.
There are two general types of pollutants:
- Particulates
- Dust from fibrous materials (carpeting, clothing)
- Hair, skin and fingernail sheddings
- Smoke/soot
- Oil burning furnaces or fireplaces
- Kitchen cooking
- Gases
- Newly applied oil-base paints
- Wood
- Adhesives
- Sulfur from rubber products, wood, felt
- Chlorides from sea air
Poor air quality and other pollutants can disintegrate, discolor and corrode artifacts. Air quality is a key factor in keeping a collection protected.
Make sure air filters are clean, intake vents are not placed near idling vehicles, windows are closed and material is stored in archival-quality enclosures.
Archival-quality storage enclosures protect objects from a less-than-perfect environment by slowing air exchange, thereby buffering temperature and humidity fluctuations, cutting down on UV exposure and providing protection against water and other damage.
Light
There are three types of light that can damage artifacts; ultraviolet, visible and infrared.
All damage caused by light is permanent and cannot be reversed.
- Ultraviolet (UV) rays are extremely damaging to most materials. Fibers become brittle and can yellow. UV light can also fade dyes and change colors.
- UV filtering film, drapes or shades on windows will cut down UV from sunlight. Placing UV filtering sleeves over fluorescent lights can block most harmful rays.
- Exposure time can be reduced in storage areas with timed switches or a "low light" policy.
- Visible light can also damage your artifacts. While there are filters and other ways to limit UV exposure, visible light, is unavoidable.
- Light levels should be kept as low as possible while still enabling visitors to view objects on display. It is recommended that levels range from 5 to 15 foot candles, depending on sensitivity.
- Limiting the amount of time items are exposed to light is also important. Plan your exhibits so that items can be rotated and returned to dark storage to prevent fading.
- Infrared (IR) light is a common source of radiant destruction because it creates heat. Heat can cause cracking, lifting and changes in an artifact’s color.
- IR heating typically becomes an issue with two sources of light: high intensity (over 465 lux) incandescent lamps and direct sunlight.
- By limiting visible light, IR will also be limited. Monitoring temperature will make assessing IR light easier.
Physical Damage
Cumulative or catastrophic, physical damage often permanently alters an object.
There are five force-related effects:
- Impact
- Shock
- Vibration
- Pressure
- Abrasion
Physical damage can be caused by general use but also by accident. Catastrophic events, such as earthquakes, should be include in your emergency response plan.
Cumulative damage can be difficult to determine, but should not be overlooked. Establish procedures to protect items from damage caused by vibration or abrasion.
Fire
Fire is the most destructive and immediately damaging source of deterioration.
A fire can be catastrophic and damage artifacts past the point of recovery. Surviving artifacts still can be damaged by heat, soot and ash.
Determining a museum’s vulnerability to different events that cause fire can allow for appropriate procedures to be put in place. Fire prevention is an important part of any emergency plan.
A majority of fires are a result of neglect or intentionally set.
Water
Water damage can be caused by a variety of events: weather, roof leaks, plumbing, spills, firefighting, and even accidents.
Water causes organic materials to swell, stain and discolor artifacts, and weaken hinges and mounts. It also provides the environmental conditions that produce mold and rust.
Plumbing leaks can deposit sewage and other contaminants on items.
Keep track of necessary maintenance to avoid building-related leaks. Create an emergency response plan specifically for water-related events.
Criminal Risk
Theft
There are three common types of theft - intentional, opportunistic or malicious.
Theft by someone within an organization is more common than theft by external parties. Instituting internal screening procedures and documentation practices can discourage internal theft.
Vandalism
Vandalism is typically an opportunistic crime that is committed randomly without planning or clear rationale. Sometimes, vandals can target certain artworks as an act of protest or due to particular prejudice.
Creating a mandatory bag check or inspection can deter vandals.
Pests
Microorganisms, insects and rodents are the majority of pests affecting artifacts.
Organic materials, such as furniture, books, papers, feathers, textiles and plant materials, are the most vulnerable to damage by pests.
Signs that you may have pests include:
- Presence of adult pests and their frass, larvae or eggs
- Accumulation of powder
- Damage including
- Holes
- "Grazed" surfaces
- Staining
- Structural weakening
- Loss of material
Continually monitoring a collection should alert staff to potential pest issues. Design an Integrated Pest Management (IPM) program to eliminate and prevent pests.
Dissociation/Custodial Neglect
This is the only agent of deterioration that does not cause physical damage.
Custodial neglect occurs when active care is not taken to preserve the collection or when information and practices are not current.
Dissociation results in the loss of objects or object-related data, or the ability to retrieve or associate objects with data. This affects the intellectual, cultural, and legal aspects of an object.
By maintaining meticulous records and establishing a procedure for labeling objects, the effects of dissociation and custodial neglect can be dramatically diminished.
Want to learn more?
- Agents of Deterioration © Canadian Conservation Institute
- Agents of Deterioration Video Playlist - Dig It With Raven
- Collections Care Basics Webinar- Documentary Heritage & Preservation Resources
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