Agents of Deterioration
All materials can be degraded by the devastating effects of fire, but paper is arguably the most vulnerable. Crowded storage areas and outdated electrical systems contribute toward a risk of fire. Well-maintained fire suppression systems and regularly up-dated disaster planning can mitigate the risks of fire.
Fire-related disasters also often include exposure to large amounts of water. This, as well as flood conditions, are most threatening to paper and other organic media. Water alarms, good storage furniture design, and disaster planning minimize this risk.
Direct Physical Forces
Perhaps the most obvious of the deterioration agents, physical forces can cause breakage and other forms of damage, such as planar deformation. Brittle media, like glass and ceramics, are particularly vulnerable to physical damage. Also at risk are large objects, heavy objects, and outdoor sculpture. One of the best ways to limit physical damage is to minimize handling. Good handling practices, storage, and security systems are critical as well.
Heat accelerates most chemical reactions, which means that the degradation effects of other agents will progress more quickly in an environment that is too warm. Additionally, fluctuation between temperatures is very stressful for materials and can cause cracking and even breakage. All materials are vulnerable to temperature, but particularly artworks made from complex laminate structures such as frames, or materials under tension, like canvas paintings and many musical instruments. Environmental control and monitoring is the best way to combat incorrect temperature.
Incorrect Relative Humidity
The effects of incorrect relative humidity, or of aggressive cycling between different relative humidity levels, are different from the effects of liquid water. Organic materials in particular absorb moisture from the air in periods of high humidity. This can cause them to soften and even swell slightly. At RH levels above 60%, mold can grow. When the relative humidity is low, these materials contract and in some cases can become very brittle or crack. Environmental control and monitoring is essential to mitigation of incorrect relative humidity.
There are a number of insects that will feed on collections materials, and an infestation can be devastating for an institution. Some of the most common collection pests are webbing clothes moths, which eat proteinaceous materials such as wool and silk; powder post beetles, which consume wood and other cellulosics; and silverfish, which graze on paper. Particularly vulnerable collections include these as well as feathers and fur. Integrated pest management will help a collection to control its insect population, prevent infestation, and catch activity quickly.
Thieves and Vandals
High value and controversial items, such as jewelry and outdoor sculpture, are vulnerable to theft and vandalism. Security systems and collections policies are tools to prevent these.
This is the tendency for complex systems to move toward disorder, and will often manifest within collections as items becoming separated from their documentation, or from other necessary components. Vulnerable collections include large, complex groups of related objects such as dolls and clothes, place settings, or archaeological fragments. Dissociation is controlled and minimized with good collection policies and up-to-date record-keeping.
Radiation in the form of light effects materials derived from living systems, such as plants and animals, more than inorganic materials like stone and ceramic, although there are some exceptions. Particularly vulnerable collections include fragile textiles, watercolors, and artifacts with natural dyes. Silk and Asian lacquer are two specific materials that are very sensitive to light. Light damage is cumulative and irreversible, but can be managed with environmental control and monitoring, and well-designed storage enclosures.
Pollutants can cause degradation through physical contact, as dust settling on a surface, or chemical reaction, such as when silver reacts with sulfur in the air to become tarnished. Collections can be exposed to pollutants through air handling systems, exposure to visitors, and from contact with one another. For example, leather can become acidic as it ages and contact with acidic leather may cause glass beads to crack and break. Environmental control and good storage and display conditions mitigate the effects of pollutants.
Preventive conservation activities include environmental control and monitoring, integrated pest management strategies, security systems, storage and display, disaster response preparedness, and safe handling techniques. The MACC preservation services department provides consultation and training in all these topics to help assist you and your collection.