Conserving, Preserving, and Restoring Your Heritage. Kennis Kim
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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 pellionella Linnaeus) and the web making moth (Tineola bisselliella Hummel). Web making moths lay eggs singly or in small groups within the fibres of the infested material. The eggs are secured to the infested material with a gelatinous excretion. The emerging larvae spin webs consisting of fibres from the infested support and feces. The webbing, often in a tubular form, spreads as the larvae travel across the fabric.
Case making moths have habits similar to the web making moths except that the larva spins a case of silk that is interwoven with fibres removed from the support during feeding, but the case is not attached to the support material. The larvae drag their cases with them and will die if the case is removed.
Vacuuming, freezing, and cleaning are all methods to control moth infestations without fumigants (see Appendix 11: Treating Infestations in Textiles by Freezing).
There are many other insects and rodents that will attack collections. If an infestation is suspected, it is best to try to capture a sample of the pest to determine the most appropriate methods of controlling the infestation.
Rodents
During spring and fall, it is quite common for rodents such as mice, rats, and squirrels to try and find a way into your home. Raccoons and opossums like to find winter refuge in attics, garages, and other outdoor storage structures. Rodents destroy and damage artifacts by feeding on them or using paper and fabrics, especially furniture stuffing, as nesting materials.
Once a rodent has found its way into a space, it tends to return repeatedly. If young are born, they too can return seasonally unless entry is prevented. It is best to store your artifacts within your living space where infestations are less likely to happen and, if rodents do enter, the infestation will be discovered quickly.
CHAPTER 2 Paper, Parchment, and Vellum
Most manuscripts, legal documents, ullic records, diplomas, drawings, and many other two-dimensional artifacts are created on paper, parchment, or vellum. Paper is produced from the pulp of wood; parchment and vellum are made from the un-tanned skin of animals. In the Middle Ages, the term vellum was used to describe fine parchment. Vellum was sometimes dyed a rich purple for very important documents.
Preservation Concerns
The preservation