Conservation and restoration of books

1. Agents of deterioration

Conservators must have knowledge of agents that cause decay in order to preserve items.^[11] Agents of deterioration can include mishandling, light, fluctuating humidity, dust and pollution, fire, water, gas and heat, neglect, and pests and other vermin. Inherent vice is "the quality of a material or an object to self-destruct or to be unusually difficult to maintain". Paper, books, manuscripts, and ephemera are prime examples of materials subject to inherent vice. Early paper was handmade from plant fibers such as flax, hemp, and cotton which are durable and can last for centuries.^[2] In the mid-19th century, machine-made paper was introduced, and wood pulp became the most common, least expensive ingredient in paper, especially in newspapers. The presence of lignin in wood pulp paper causes acid to degrade the cellulose, which causes the paper to become brittle and discolored over time.^[35] In addition, paper has the natural ability to absorb and retain moisture from the atmosphere, making it prone to the growth of mold, fungi, and bacteria.^[36] Furthermore, some inks used in old books and manuscripts are harmful to paper. Iron gall ink, most commonly used from the 8th century through the end of the 19th century, contains acid and can corrode the paper in humid conditions.^[37]

Mishandling

Poor handling is the primary cause of deterioration for books, manuscripts, and ephemera; however, a poor environment can also be a cause of deterioration for books and paper.

Pests and other vermin

Insects and vermin are naturally attracted to paper because paper is made of cellulose, starch and protein, materials that provide sources of nourishment.^[36] The most common pests are roaches, silverfish, and various types of beetles.^[39] Book lice feed on mold spores found on paper and cardboard, and although they do not cause visible damage, their decomposition and excretions can stain paper and may also nourish other pests, continuing the cycle of damage.^[2] Freezing collection items can mitigate pests.^[39] However, some materials should not be frozen, such as books made with leather, because the cold temperatures may cause the fat to rise to the surface of the leather resulting in a white or yellow area called a bloom.^[39] The use of insecticides directly on collection materials is not generally recommended. However, if the infestation is severe, and fumigation is the best option, the affected items should be separated from the rest of the collection for treatment.^[36]

2. Preventive conservation and storage

Storage in a cool, dry, clean, and stable location can extend the life of an item.^[51] Manuscripts and paper documents are often stored in protective archival-quality boxes and folders, made of acid-free and lignin-free materials.^[52] Documents with heavy use may be stored or encapsulated in a clear polyester (Mylar) film sleeve or folder. As added protection against acid formation, paper-based storage materials may have a buffer, such as calcium carbonate, which can neutralize acids as they form in the storage materials.^[52] Boxes should not be overfilled. Items may be interleaved with acid/lignin-free paper.^[43] If boxes are only partially full, spacers may be used, or the box may be stored horizontally.^[2] Large format material is best stored in a plan cabinet with shallow drawers.^[43] The rolling of large items (e.g. maps) should be avoided where possible; but if there is no other option, the item should be rolled around a large diameter archival quality tube.^[53]

Average-size books should be shelved vertically, side-by-side so they can support each other.^[51] Shelves should not be overpacked and should stand away from exterior walls. Oversized or fragile books may be stored horizontally and completely flat, but stacking should be kept to a minimum.^[37] Books may be placed in supportive and protective boxes, to prevent soiling and abrasion and to provide structural support. Book boxes may range from simple four-flap enclosures made of archival safe paper or cardboard to custom clamshell or drop-spine boxes covered in book cloth.^[51]