Paper acid-deterioration: the era of bad paper


The life of paper sometimes does not depend on its age but other factors, such as papermaking materials, the process of papermaking or storage environments. Deterioration of paper is a complex and difficult problem. The most common paper deterioration is acidification, which makes paper become yellowed and brittle. Generally speaking, good quality of paper can be preserved for decades even hundreds years long. What is the difference between high and low quality of paper? What makes some paper deteriorate rapidly? Understanding well enough for paper deterioration to control them is the responsibility for library professions, archivists and paper manufacturers. This paper is mainly focus on acid deterioration of paper. Through the history of papermaking and different compositions of paper during mid-nineteenth to twentieth century can be more understanding of the severity of the acid in the paper.


One of the missions for library professions is to protect library materials, which contain a vast majority of organic substance and thus subject to variety of deterioration, and the other mission is to control deterioration well enough so that library materials can fulfill their function for as long as they need. According to the Library of Congress, “Why is 500-year old paper often in better condition than paper from 50 years ago? ” (“The Deterioration and Preservation of Paper: Some Essential Facts.” n.d.). In other words, why are the older the paper not in the worse condition than the younger one? What makes the rate of paper deterioration is different? Mary Lynn Ritzenthaler (1993), a chief of the Document Conservation Laboratory claims in her book “Preserving archives and manuscripts” that “The period from 1850 to the present has often been considered the era of bad paper.” (p. 23) It might show that the quality of paper after the mid-nineteenth century has changed and become worse. Not only the proper storage environment can effect the longevity of paper, but also the progress and materials of papermaking. The purpose for this research paper is to understand the history of papermaking, paper deterioration, and the solutions to extend the useful life of paper items.

One news on Library Journal in 1991 found the following:

“Acid Free Becomes Law: On October 12, 1990, President Bush signed PL 101-423 into law, making it the official policy of the United States that federal records, books, and publications of enduring value be produced on acid-free permanent papers.”

It could indicate that using acid-free papers is a good choice for records, publications and books, which may endure longer time. Before understanding the importance and the characteristics of acid-free papers, we need to know what acidity is. In pH scale, the number 7.0 is being the point of neutrality. All numbers above 7.0 represent increasing alkalinity, and all numbers below 7.0 indicate increasing acidity. However, how does the acidity affect paper? Senator Claiborne Pell (1998), chairman of Congress’s Joint Committee on the Library, says that “… It should be noted that the implementation of the national policy, by attacking the problem prospectively, will have the effect of reducing the long-range costs of deacidification. Every book produced on acid-free paper today frees up preservation resources which can be used to attack the crumbling backlog of publications dating back to 1850.” In other words, if using acid-free papers broadly, the government agencies can save a lot of money on the mass paper deacidification treatment, which is the process to increase the pH of acid paper and significantly slow the rate of paper degradation. Therefore, since 1990 or earlier, preservation specialists have aware of the importance of acid-free paper and looked for the cost-effective preservation method.

Papermaking history

To understand the nature of support material, which will determine the way it behaves, can help us to find out the best way to protect and preserve it. The first papermaking process was documented before the first century BCE. Before the Papermaking machines were invented in the early 19th century, all paper was made by hand. In the book “The preservation challenge: a guide to conserving library materials” written by Carolyn Clark Morrow with Gay Walker (1983), they indicate that machine-made paper was well established by the 1830s. However, with the increase demand for printed works and the chronic shortage of suitable papermaking fibers, the quality of paper has changed. The certain fibers in early papermaking process are cotton, linen clothing rags and by a process that largely preserved the long fibers of the raw material, which made the better and more durable papers. By the 1850s, the shorter and cheaper fibers—ground wood, replaced rags as the raw material for paper manufacture and produced by chemical and mechanical pulping processes. “Many of the technological improvements, however, resulted in paper that was destined to deteriorate rapidly.” (Morrow & Walker, 1983, p.23-26)


Apart from the component of fibers may influence the feature and the life span of paper, the chemical pulping process and other manufactures may cause paper acidified, which is a big challenge for paper preservation. Ritzenthaler (1993) claims that “Acidity causes paper to lose its strength by hydrolysis of its cellulose molecules; the polymer chains gradually break down and the paper becomes weak, brittle, and disclosed.”  (p.23). According to the other article, Smith (1975) indicated that “Paper degradation is largely due to the acid hydrolysis of the glycosidic linkages in cellulose.” (p. 200). It could say that the acidity may seriously destroy the length of structural chains of fibers and cause yellowing and embrittling due to the chemical effects. Yet, where does the acidity come from? Ellis (2017) talks in her book “The care of prints and drawings” that “Acid may be internal, that is, a result of the papermaking process, or external, that is, introduced by migration from other acidic materials or atmosphere pollution.”(p.224). Starting from the1850s, the increased use alum-rosin sizing to reduce absorbency and minimize bleeding of inks. However, the alum-rosin, which generates sulfuric acid in the presence of moisture, had become widely used as a replacement for more expensive gelatin size. The other factor is the residue of chlorine bleaching, which is used to clean the dirty during the process. Other sources of acid from external include acid migration and atmosphere pollution. “Acid migration (or transfer) refers to the ability of acid to move from an acid material to item of less or no acidity. This transfer takes place through direct contact with adjacent acidic materials (for example, secondary materials such as manila file folders as well as poor quality papers such as newspaper clippings), or through exposure to acidic vapors in the surrounding environment (such as a closed box or file drawer).” (Ritzenthaler, 1993, p.23) .In addition, acids also form in paper by the absorption of pollutants, book leaves that are more brown and brittle along the edges than in the center clearly illustrate this situation. The major acid atmosphere pollutants are sulfur dioxide (SO2) and nitrogen dioxide (NO2), which are
ubiquitous in urban air worldwide. Acid from the environment and from within the paper in the presence of moisture, reaction products in the atmosphere and on surfaces include sulfuric acid (H2S04) and nitric acid (HN03), cut the glucose chains into shorter lengths. This acid hydrolysis reaction produces more acids and continued contributing to the degradation of paper. (Williams & Grosjean, 1992, p.200)

Acid-free and permanent paper

The period from the mid-nineteenth to mid-twentieth century is considered a bad era for paper, but how to produce higher quality of papers in order to last the long time is an important problem. By controlling the following factors: quality of source; fiber length; pH; sizing; residual chemicals and adjacent environments is possible to make durable and permanent papers.


Paper is made of cellulose, which is the main chemical constituent of the cell walls of plants. “Cellulose is what makes the whole thing work. Chemically speaking, cellulose exists as atoms of carbon, hydrogen, and oxygen joined together in arrangement of C6H10O5 and connected one to another to form long chain molecules called polymers. The molecular structure of cellulose makes it ideal for papermaking, since a mass of long, intertwining fibers orderly arranged in parallel and stacked sheets of cellulose polymers has great strength and flexibility. Furthermore, when in proximity with other cellulose molecules, both the polymer itself and its neighbor are stabilized and their attraction further strengthened by an electrochemical property know as hydrogen bonding.” (Ellis, 2017, p.14-15)

Acid-free and permanent paper

Acid-free is the paper industry’s designation for any paper produced with a neutral pH 7 that contain no acid pulp. “Acid free has become almost a generic term used to denote a board range of desirable characteristics of archival storage materials.” (Ritzenthaler, 1993, p.23) It could mean that the paper without acidity is the ideal method for archival materials and has become more and more prevalent. Since 1992, the National Information Standards Organization published a standard ANSI/NISO Z39.48-1992 (R2009)—“Permanence of Paper for Publications and Documents in Libraries and Archives.” “This standard establishes criteria for coated and uncoated paper that will last several hundred years without significant deterioration under normal use and storage conditions in libraries and archives. This standard identifies the specific properties of such paper and specifies the tests required to demonstrate these properties.” (National Information Standards Organization, 1992)

There are two additional specific terms about acid-free paper. The first one is archival paper, which is often used in misleading manner by paper producer.  “Archival” originally meant “pertaining to archives or records; or contained in records”. (Balloffet& Hille, 2005). Therefore, when we hear archival materials, it is difficult to distinguish between physical papers or documents. The other term is permanent paper, which is referred to as acid-free paper, but not all acid-free paper meet the standards for permanent paper. In 1994, there is another similar international standard for permanent paper, ISO 9706 published. If the paper meets ANSI/NISO or ISO standards could be labeled as permanent paper with the infinity symbol. This symbol can be seen on permanent paper or books that have printed on permanent paper. However, the acid-free is determined at the time of manufacture and does not mean that the material will maintain a stable pH over time. A research from the Library of Congress indicates that the reason why acid-free (neutral) paper become increasingly acidic as they age. Not only because of the acids contains within weeks of the paper’s manufacture, but also the paper rarely release these acids due to strong intermolecular bonding.

Alkaline Buffered paper

In order to preserve significant historical records and books, neutralizing the acid on paper with an alkalizing agent has become a protection approach. The alkaline reserve could be an alkaline earth salt like magnesium carbonate or calcium carbonate, which has pH in the range of 8.5-10.0. Morrow (1983) claims that in 1959 at the Standard Paper Manufacturing Co. in Richmond, VA where the test run of alkaline paper produced. At the same time, the number of acid-free paper has been gradually increasing. Until 1980, approximately 25 % of the book paper manufactured in the United States was acid free. In addition, paper producers started to add alkaline buffers, which retard and prevent acid hydrolysis by neutralizing acids, into wood pulp papers. Nowadays, this method has become common practice. (Morrow & Walker, 1983, p.23-26). Alkaline wood pulp papers stored under good conditions (cooler temperatures and 30-40% relative humidity) are long lasting, even hundreds of years.


The history of Papermaking is a long story and the composition of paper is constantly changing. Since the mid-nineteenth century, after papermaking machine appeared, the paper raw material shortage and chemical substances involved, the quality of paper became worse. The acidity of paper has a direct impact on library’s collections. Acid may come from internal like papermaking progress; and external like acid-migration and atmosphere pollution. In order to slow down acid deterioration of paper, there are two international standards to take care of the properties of papers and establish criteria for paper manufacturers. By early twentieth century, paper manufacturers have began producing Acid-Free paper and Alkaline-Buffered paper to let paper be long lasting.


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