Causes of Deterioration of Paper

Nimfa R. Maravilla

Nimfa Maravilla (nee Rubias) is a chemical engineer who joined the National Historical Institute's (NHI) Materials Conservation Center (MCC) in 1984. NHI is cultural agency under the National Commission for Culture and the Arts (Office of the President) in the Philippines. In 1985, she attended the First Paper Conservation Course at the International Centre for the Study of the Preservation and Restoration of Cultural Property (ICCROM) in Rome, Italy. She is the founding vice president of the Philippine Association for Scientific Conservation of Cultural Property, Inc. (PASCON). She headed the NHI-MCC from 1987 to 1994 and was Officer-In-Charge of NHI's Monuments and Heraldry Division from 1994 to 1999 prior to her migration to New Zealand.

The materials of which library and archive collections are composed, namely paper, parchment, palm leaves, birch bark, leather and adhesives used in bookbinding, are susceptible to two main forms of deterioration. One is biological deterioration caused by insect attack and/or fungal growth, and the other form of deterioration is caused by adverse environmental conditions such as extremes of dampness or wide fluctuations in relative humidity associated with large variations in day and night temperatures, light and atmospheric pollutants. These two forms of deterioration are interconnected because humid conditions favor the growth of fungi and accumulations of dust and dirt will attract insects.

Biological Factors

Where there is condensation or moisture due to high humidity, there is always the presence of biological growths such molds or fungi, insects and rodents causing infestation. Biological agents attack paper and other organic materials when both temperature and humidity are uncontrolled. Mold spores remain suspended in the air until they find suitable conditions for their growth. If mold is observed in the collection yet environmental conditions are not altered to halt its proliferation, the mold will digest the material on which it has begun to grow. This results in the staining and deterioration of materials attacked and in rapid loss of strength of organic materials. The growth of fungi is revealed by the formation of whitish patches on book covers and documents, which later may become brownish or greenish in color. It is a common experience to note that this mold growth occurs more readily on items made of organic materials that are tightly packed, and this is due to the fact that a thin, stagnant pocket of moist air is formed which favors mold growth.

In addition to high temperature and humidity, man's negligence also favors the growth and proliferation of insects. The following manifests such negligence:

Rodents and insects are the worst enemies of books and other organic materials that are cellulose in nature. The materials contain proteins and carbohydrates in the form of sizing, paste or starches, and other organic substances attractive to insects. The nature and extent of the damage depend not only on the insect and material, but also on how promptly the infestation is discovered and controlled. Damage may vary from a few holes to complete destruction.

Deterioration of Paper Caused By Insects

The most common types of insects that attack paper objects are:

Termites are small, yellowish or whitish social insects that live in wood and under the ground. They live under conditions in which humidity within the colony is maintained at a high level. In books, they produce deep, crater-shaped holes, or deep, irregularly shaped erosions; sometimes this leads to almost total destruction of the volume and bring about irreparable loss or damage.

Silverfish are wingless insects with long antennae and usually with three (3) long, tail-like appendages that are of silver-gray color. They are usually found in moist locations, that is, under stones and boards, cracks and crevices or in dark places where humidity is greater than 55%. This type of insects cause superficial damage to paper of irregular outline, but much smaller than that caused by cockroaches, especially the glossy type, books and documents, and wallpaper, and, eats away glue, paste, etc.; also attacks photographic plates and gelatin.

Cockroaches are nocturnal insects that have reddish brown color and fetid odor. Cockroaches hide in warm, damp and dark places like the bathroom, floors of kitchen, under the sink, near water pipes, crevices, cabinets and cupboards. They cause superficial erosion of irregular outline; a blackish "comma" shape mark on paper is a positive indication of the presence of cockroach.

Booklice are small soft-bodied insects that have relatively large heads, fairly long antennae and strong-toothed mandibles. Booklice cause tiny superficial erosions of irregular outline to paper, leather, gelatin of photographic plates, watercolors, parchment, glue and gum of bookbinding.

Case-bearing clothes moth thrives in undisturbed and unventilated areas that destroy bookbinding.

Powder post beetles have leathery front wings forming a sheath for the membranous underwings. They have long antennae of various shapes, 2 to 5 mm long and dark red to black in color. They bore holes into books and other organic materials.

Deathwatch beetles winding, circular tunnels which generally extend from the edges to the book's center; the mixture of eroded material and feces that fills the tunnels is known as "frass".

Carpet beetles cause irregular perforations and sometimes surface tunnels containing powdery excrement and cast-off larval skins on books and other paper organic materials.

Temperature and Relative Humidity

Temperature and relative humidity have been shown to be interdependent. Hygroscopic materials that normally contain moisture are the most sensitive to over-drying. These hygroscopic materials are those of organic origin and of fibrous or cellular structure, such as paper, parchment, papyrus, leather and notably the adhesives used in bookbinding. Paper and related materials, on the other hand, deteriorate rapidly with temperature and relative humidity changes.

The greatest danger that can arise from an excessively high relative humidity is the tendency for molds to grow on any material that can provide nutriment, such as glue, leather and paper. The presence of mold growth is a warning that the atmospheric relative humidity is above the limit of safety. If too high, humidity hastens acid deterioration. When conditions are favorable to mold growth, for example, in a library, a gray dusty bloom is observed in the first instance on the darker bindings, and it soon becomes fluffy with a tendency to be organized in circular patches.

There are some evidence that regular changes in temperature and relative humidity (cycling) can lead to weakening of paper and related materials, as a result of internal stresses set up in them in response to these changes. There are no firm data to indicate how serious this effect may be, but scientists do not believe that it results in measurable damage to these materials if such changes in temperature and relative humidity can be held to less that 10 degrees and 15%.

Light

Apart from other causes earlier discussed, light can, to a large extent, be regarded as an independent and prime cause of deterioration of museum objects. The type of materials forming part of the museum collection that are subject to damage by light are pigments and dyestuff, including inks; paper and other cellulose materials; and, various other organic materials.

Pigments and dyestuff fade when exposed to light and this is very noticeable in water colors. Unfortunately, colors fade selectively, some disappearing while other remain unchanged, which means that the color relationships of a painting can be grossly distorted.

Rapid and serious deterioration of paper is caused by the oxidation of cellulose brought about by the ultraviolet rays in sunlight and fluorescent light. There are two effects of light on paper that result in its ultimate embrittlement and deterioration. First, it has a bleaching action that causes some whitening of paper and fading of colored papers and certain inks. Second, it causes any lignin, which may be present in the paper, to react with other compounds and turns it yellow or brownish. It is this reaction that results in newspapers' turning yellow on exposure to light. Certain invisible changes also occur at the same time when these visible effects of light are taking place. Fibers in the paper are broken into smaller and smaller units until they are so short they can no longer maintain the bonds necessary to hold the paper together. Some woods bleach under the action of light; some turn "yellow" and some darken. Unfortunately, the reactions initiated by light continue after the source of the damage has been removed.

Atmospheric Pollutants

Materials of organic origin such as leather, parchment and artifacts in which cellulose fibers such as paper products form the support are likely to be soiled and stained by solid particles of carbon, tarry matters and other solid contaminants. The worse contaminants for this group of materials are sulfurous and sulfuric acids resulting from the combustion of fuels and from other industrial processes. The effects are severe with cellulose materials such as paper and leather. There is a close correlation between the loss of strength of paper and its acidity resulting from sulfuric acid contamination. Dust and dirt particles in the air not only carry with them the adsorbed pollutants mentioned above but may exert an abrasive action on books and paper.


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URL: http://cool.conservation-us.org/byauth/maravilla/deterioration-causes.html
Timestamp: Sunday, 23-Nov-2008 15:20:17 PST
Retrieved: Tuesday, 30-Sep-2014 21:54:20 GMT