to the artifact.
To reduce damage from visible light, you should reduce the amount of daylight and glare from glossy surfaces to produce lower light levels acceptable for viewing. This can be achieved by indirect lighting: either reflecting light off another surface or lighting from an angle. Light damage is cumulative and depends on the intensity of the light level as well as the length of exposure. Rotate light sensitive items that are displayed so that artifacts will have time to “rest” in dark storage.
Temperature
Heat, cold, and cycling of temperatures cause damage to artifacts. When an artifact is warmed, the rate of chemical reactions within the molecular structure increases. These reactions are the deterioration of the artifact. Ambient temperature and exposure to IR light sources such as daylight, incandescent lamps, or spotlights cause warming of an object. Darker objects absorb more energy and warm quicker than lighter surfaces. If an object heats, cools, or cycles through rapid changes of temperature of more than 10 degrees within a short period of time (one to two hours), the result can be significant dimensional change: expansion and contraction.
Relative Humidity
Relative humidity (RH) is a percentage representing the amount of water vapour in the air compared to the total amount of water the air can hold at that temperature. A relative humidity of 100 percent at a given temperature would refer to complete saturation of the air by the water vapour present.
Changes in the RH do not greatly affect most people’s comfort level but a temperature change of a few degrees does make a difference in how comfortable you feel. Art and artifacts react much more to changes in RH than shifts in temperature. It is much more important to stabilize the RH levels than the temperature for the stability and long-term care of objects.
Damage seen at RH 70 percent and above:
• micro-organisms: mould and mildew
• deformations from plane as a result of tension loss
Damage seen at less than 35 percent RH:
• shrinking
• warping
• cracking
• drying out of adhesives
• desiccation
Cycles of RH with changes of more than 5 percent an hour result in expansion and contraction that lead to:
• cracking
• warping
• splitting
• water staining due to condensation
• separation of component layers
• deformations from plane (when an artifact undulates, warps, twists, or distorts causing it no longer to be flat or in its intended shape)
The environment plays an important role in the overall stability and preservation of an artifact. Unfortunately, much structural damage is a result of infestations, poor handling, and human error (see Appendix 4: General Rules for Handling and Moving Artifacts and Works of Art).
Insects and Rodents
Insects
The most common insects found in home collections are the book-lice or paper lice, cockroach, silverfish, firebrats, moths, and carpet and cigarette beetles. It is always best to try and prevent an infestation rather than have to control one, but insects are a common problem. Whenever possible, attempt to use deterrents and mechanical means of controlling an infestation before applying chemicals that could potentially be harmful to the artifacts or humans.
Book-lice (Liposcelidoe) are also known as paper lice. This almost microscopic insect normally lives outdoors feeding on microscopic moulds growing in damp situations. They have no wings but can enter buildings carried on papers, furniture, or boxes that may also be supporting mould growth. Once introduced, book-lice become numerous, especially in the late summer when both the temperature and relative humidity are high. In addition to feeding on mould, they feed on the adhesives in books and wallpaper, as well as cereals and paper products, but do not seem to cause holes as with silverfish and roaches. They are transparent to grey in colour.
Control of an infestation is difficult since book-lice are numerous and easily reintroduced to a collection. Book-lice do not need males for reproduction and can produce up to eight generations a year. Twenty to 90 eggs are laid and hatch in 6 to 21 days. Reduction of humidity will reduce the presence of book-lice.
Cockroaches belong to the insect order Blattaria. Roaches are primarily nocturnal. They breed throughout the year. Eggs are laid in batches of 18 to 50 per capsule and are carried by the female until close to hatching time, about 14 to 30 days. Roaches are able to squeeze through very narrow openings and are good climbers. They feed on books, paper, bindings, adhesives, and any other starchy products. Damage from feeding appears as holes or notches. In addition to the damage caused by chewing, roaches cause a great deal of staining as a result of vomiting, depositing feces, secreting fluid from their abdominal glands, or adhesion of egg casings.
Control of a roach infestation is best done by improved sanitation, minimizing water and condensation, and discarding excess paper and cardboard. When storing artifacts, change wooden storage furniture to stainless steel and, as a deterrent, place paper products in plastic containers rather than paper or cardboard.
If roach infestations recur, you may need to take additional measures. Replace hollow doors with solid core, install insect-proof outlets, store all food products in plastic containers, and seal access between rooms and floors (such as via plumbing and electrical wiring). Non-chemical sticky traps placed directly against the wall near water sources can control an infestation, but fumigation, insecticides, or baits may be required.
Silverfish (Lepisma saccharina) and firebrats (Themobia domestica) have very similar characteristics and feeding habits. The primary difference is that silverfish prefer cool damp conditions and firebrats like hot and humid conditions. The silverfish lays about 100 eggs singly or in groups of twos or threes. Firebrats lay about 50. Adults of both may live two years or longer. Both insects eat carbohydrate and protein-rich foods including fabrics, papers, and adhesives. They particularly like the sizing applied to paper and fabrics during processing. Common evidence of damage includes holes and notches as well as what appears to be scraped or thinned paper.
You can control an infestation mechanically by lowering the ambient temperature. If possible, freezing will kill firebrat nymphs. Using plastic storage containers, reducing the humidity, and increasing light will deter these insects. You may need to use sticky traps, fumigants, or insecticides.
Carpet beetles (several species) and cigarette beetles (Lasioderma serricorne F) are serious threats to books and textiles. It is the beetles’ larvae that cause the most damage to collections as they feed on upholstery, stuffing, dried flowers, fabric, wood, paper, and adhesives.
Dry cleaning or vacuuming infested fabrics, furniture, and books can help control an insect problem. Freezing for 72 hours is a proven method of killing some beetles. Capture a specimen to determine a course of action. Chemical extermination may be required.
The most common clothes moths are the case making moth (Tinea
