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Chapter 7
Paper Permanence Research in the United States

The Swedish Model in the United States

Work done at the Swedish Government Testing Institute in Stockholm was influential in paper chemistry in general, and especially so in permanence research, affecting chemists world wide. in the United States, chemists at the National Bureau of Standards (NBS) replicated and expanded upon this Swedish research. This research, filtered through the NBS, formed Barrow's conception of paper deterioration. in Stockholm, Köhler and Hall carried out a series of studies on paper deterioration during the 1920s. The findings of this research are here referred to as the Swedish Model for convenience of expression (Conroy 1991, 1).

Köhler and Hall's research was extensively translated, published, and summarized in the chemical literature. The methods they pioneered were ultimately adopted by the Technical Association of the Pulp and Paper Industry as standard methodology in use to this day. They were the first to use artificial or accelerated aging by light or heat to study systematically the dynamics of paper deterioration. Accelerated aging was used as one among several indications of paper stability. It was accomplished by heating samples of new paper for various lengths of time at 100°C. the previously heated samples were then compared with control samples. These comparisons could be made quickly, in days rather than years, as is necessary with natural aging. Comparisons were made of both physical and chemical properties of paper; for example, chemists studied the relative effects on permanence of residual acidity (a chemical property) and, for example, tensile strength (a physical property). Hall measured the pH (a chemical property) of paper. The level of pH corresponds to the degree of acidity or alkalinity of the paper; extreme amounts of either are associated with rapid deterioration of paper (Hall 1926).

In addition to methodological advances, the Swedish research also clarified important concepts in paper chemistry. Köhler and Hall were the first to distinguish durability (the ability of paper to keep its original characteristics in use) from permanence (the ability of paper to retain its original characteristics over time). Previously, 'characteristics under use' and 'longevity of characteristics' were not separated, but conceptualized in combination so that durability meant 'strength in use over time'. the distinction between permanence and durability enabled chemists to study, for example, the strength of new paper as one of paper's original characteristics that could be affected by the passage of time (Conroy 1984, 1). "'Durability' of paper involves its capacity to preserve its original properties when in use ('physical durability') and its capacity to preserve its original properties when being stored or kept under normal conditions ('chemical durability' or permanence). The physical durability depends on the physical properties of the paper, and the chemical durability is dependent chiefly on the chemical properties" (Hall 1926, 58). This research also promoted the use and eventual standardization of the folding endurance test as a standard measure of paper strength.

Köhler and Hall detailed the dynamics of rapid deterioration of modern paper in terms of their new measurements, conceptual distinctions, and were perhaps the first to mention filler as producing a possible increase in permanence.

Rosin sizing causes a decrease in the folding resistance and an increase in the acidity of the paper as compared with unsized paper; . . . deterioration in durability due to rosin sizing is probably not sufficient to render rosin sizing unsuitable for paper intended for keeping indefinitely, provided excess of aluminum sulphate is avoided....sizing with animal glue increases the folding resistance as compared with unsized paper, but the increase is lost comparatively rapidly on exposure to light or heat or both and on storing at ordinary temperature; . . . the degree of acidity of tub-sizing within the limits generally accepted in practice has little or no effect on the durability of the paper; . . . the purer the cellulose (i.e., the higher the alpha cellulose content and the lower the copper number of the pulp) the higher the degree of permanence of the paper....Use of a moderate quantity of chemically inert mineral fillers seems to exert a beneficial rather than a detrimental action on the permanence (Köhler and Hall 1925, 420).

One of the areas in paper chemistry most misunderstood by non-chemists is the relationship of fiber source to permanence. Cotton fiber from rags, for example, is strong and flexible, just the characteristics that make a durable paper. If it is manufactured so that excessive amounts of residual acids are not found in the sheet, it can also be permanent. If during its manufacture excessive amounts of acid are added to the sheet, for example, from alum added to pulp before sheet formation, or alum rosin size added to pulp or sheet, even cotton fiber paper will deteriorate rapidly. Wood fiber is not as strong as cotton fiber. in addition, wood fiber requires more processing with caustic chemicals to free its cellulosic components for papermaking. This necessary chemical processing can further weaken wood fibers. However, wood fiber can be manufactured without excessive acidity or overly weakened fibers; and in that way, it can be used to make a permanent paper. If all manufacturing variables are correct for the production of permanent paper, then cotton fiber paper will be more durable and permanent than wood fiber paper because of the characteristics of cotton fiber.

Control of acid and the use of a strong and flexible fiber are not the only manufacturing requirements needed to produce a permanent paper. The process used to purify wood fibers also contributed to paper's permanence characteristics. Hall's research supported fiber source as well as the conditions of manufacture as important elements in paper permanence. "The folding resistance of bleached sulphite paper [from wood fiber] falls off much more rapidly under the action of heat or light than that of rag paper [from cotton fiber], indicating that sulphite papers [from wood fiber] are less permanent" (Hall 1926, 57). According to Banks, sulfite paper may be less permanent than other kinds of chemical wood pulp paper because the sulfite process degrades fibers (Banks 1995). Last but not least, the differences in permanence of paper made from different chemical wood pulps was sometimes misunderstood or left out of oversimplified research applications such as Barrow's (see Chapter 11).

Research on the effects of manufacture, chemical processing for fiber purification, and especially fiber source have been battlegrounds between manufacturers of cotton fiber paper and the much larger group of manufacturers of wood fiber paper. The effect of some of this conflicting research, especially as described by Clapp (Clapp 1971, 238-239, 244-245) has been to obscure the facts about paper permanence rather than clarify them. Paper is complex. There is no single simple reason, such as acid, for its deterioration, as Barrow later preached.

The National Bureau of Standards (NBS)

In the United States, much research on paper permanence was done during the late 1920s and 1930s by the NBS, which was created in 1901 from the existing Office of Standard Weights and Measures. the NBS established standards, standard instruments, tests, and analytic procedures. It determined physical constants and the properties of materials for the government and for the nation. Therefore, its scope of research in the physical sciences and its responsibility for the investigation of any problem about standards was virtually unlimited (Cochrane 1966, 43).

Samuel Wesley Stratton, first Director of the NBS, 1901-1921, modeled his new Bureau on the Reichsanstalt (The Imperial Physico-Technical Institute) at Charlottenburg (Berlin), Germany. Like the Reichsanstalt NBS was organized into two main divisions, scientific and technical, for both pure and applied research. Stratton implemented NBS's service role to the nation by accepting, without charge, inquiries from any citizen who sought technical help or information. in 1903, the NBS was moved to the newly created U. S. Department of Commerce with increased responsibility for the promotion of business and industry in the nation, and in 1904, the Chemical Research Division was added. Stratton acquired several paper mills, i.e., paper manufacturing machines, between 1917 and 1918. Thus NBS was able to manufacture paper to any specification they chose to test. The Bureau's fibrous materials division investigated the characteristics of paper. Some of this research looked for fundamental data in the properties and performance of paper, such as permanence (Cochrane 1966, 43-268).

The NBS, along with the rest of Washington, suffered major funding cuts during the years of the Depression. Both staff and research activities were severely curtailed. Nonetheless, much was accomplished by the NBS in research during this time because "Few of the professional staff had taken their imposed furloughs, preferring to work without pay, unhampered by administrative duties. Others . . . sought on their own initiative, with some success, funds from other federal agencies, in order to return to their laboratories. Looking back on those years, many at the Bureau were to have the impression that with industrial research at low ebb the period was particularly fruitful in fundamental research" (Cochrane 1966, 335).

The Depression, in this paradoxical manner, saw a renewed activity in paper research at NBS.

[Another] line of research extending earlier work, reactivated in the year of the Great Crash, was that on the permanence of paper and paper records. With funds provided by the Carnegie Foundation, studies were made of the permanence of Government writing papers, the preservation of records, and of library storage conditions. Light, heat, humidity and many other deterioratives of papers and books were assessed, . . . the investigation extended to newspaper records, motion picture film, records on photographic film, microfilm, and lamination....(Cochrane 1966, 334-335)

The NBS could and did assist small business owners with their technical questions. NBS had time to do research on paper characteristics, even those of such relatively limited interest as permanence and restoration techniques like lamination. in this way paper permanence and restoration research was, in part, a product of the effect of the Depression on government agencies. Like the engineers temporarily employed building models of ships at the Mariners Museum, the paper chemists of NBS, protected from their usual administrative directives and duties, were more free to follow their own interests. By the early 1930s, because of these circumstances, NBS was the agency that could directly assist Barrow. Like the engineers, the chemists at NBS furthered Barrow's career this time by guiding his study and answering his questions about science, technology, and research.

NBS did a series of studies that examined systematically many of the research points first pulled together by Köhler and Hall in the mid-1920s. Many of the Bureau's research studies were reported in multiple forms: the same article or different versions of the same article appearing in several journals. Also the studies were combined in summary articles and these summaries published in many technical and non-technical venues worldwide. Thus NBS expanded and generally publicized Köhler and Hall's Swedish Model of paper permanence and deterioration, and made the Swedish Model the most widely accepted modern theory of paper permanence and deterioration (Conroy, 1989, 1).

NBS started its research series in paper permanence in 1929 by replicating and verifying some of the findings of the European research. a summary concluded that the factors responsible for deterioration of samples of new paper are acidity of the paper (through hydrolysis), environmental conditions, oxygen (through oxidation), and the catalytic effect of the paper itself (Deterioration of paper 1929).

In 1930, NBS, in cooperation with the New York Public Library, published research on old newspapers dating from 1830 to 1895 finding that: "the processing of fibers is a more important factor in their aging quality than is the source of the fibers. The permanence of the papers that were made from highly-refined fibers[,] whether from rags, straw, esparto, or wood, was good, but starting with the introduction of groundwood the papers were generally badly deteriorated, whether the groundwood was associated with highly refined fibers or with only partially refined fibers such as unbleached wood sulfite" (Tests made on old papers . . . 1930, 56).

B. W. Scribner, Chief of the Paper Section of NBS, reported the extent of the topics covered in the research agenda to study paper deterioration undertaken by NBS beginning in 1930. This agenda bears a great deal of similarity to both the topics and the techniques of the Swedish Model including the use of accelerated aging and folding endurance as tests of paper permanence:

Close relations between heat resistance and cellulosic purity, independent of the source of the fibers were found. Highly refined wood fibers were found to react in the beater similarly to high-grade rag fibers. Excessive amounts of rosin and size were found to be detrimental. a permanence classification is suggested, based upon alpha content, copper number, amount of rosin, percent acidity, pH, effect of heating, and folding endurance. the effect of external influences such as acid pollution of atmosphere, light, dust, high temperatures, and high humidity are also being studied. (Scribner, "Deterioration of paper" 1930, 34)

In two other published articles in the same year, Scribner described the NBS research program to formulate definitive technical specifications for permanence qualities for paper:

A classification based on strength and purity is suggested, which places paper in the following four groups: (1) Papers of absolute permanence having a maximum degree of purity, free from unbleached fibers and highly lignified fibers such as groundwood; . . . [with] alpha cellulose 90%, copper number 1.5, rosin 1%, pH value 5; on heating 72 hours at 100° C the alpha cellulose should not decrease more than 1.5%, the folding endurance not more than 25% and the copper number should increase not more than 0.5%. (2) Papers having a minimum life of 100 years; free from unbleached fibers and highly lignified fibers such as groundwood, alpha cellulose 80%, copper number 2.5, rosin 1.5%, pH 5. (3) Papers having a minimum life of 50 years; free from unbleached fibers and groundwood, alpha cellulose 70%, copper number 5, rosin 2%, pH 5. (4) Paper for temporary use, having a low degree of purity, including papers containing unbleached fibers and groundwood. (Scribner "Permanence standards for paper" 1930, 53)

The federal government's paper purchasing specifications are based on the four categories, with later modifications, from this NBS research.

Scribner published a report describing NBS's series of permanence studies (Scribner "Report of Bureau of Standards research on preservation of records" 1931). Two more studies were published that year by NBS. Scribner, in one of these studies, again detailed the NBS's research agenda and emphasized the importance of controlling all aspects of the paper being studied including fiber content, manufacture (paper samples were made under strict controls in NBS's own mill), storage conditions, and tests. This study also concluded by detailing NBS's specifications for more permanent paper (Scribner "Bureau of Standards studies on the deterioration of paper" 1931). in the other study, NBS emphasized the usefulness of the accelerated aging test in the study paper permanence (Papers from highly purified wood fibers 1931).

Rasch, Shaw, and Bicking carried out the most important study from NBS in 1931. They examined the dynamics of the deteriorative effects of alum at each stage of paper manufacture and the mitigation of its deteriorative effects through control of its excessive use.

A definite relation between the acidity of the rosin-sized papers and their stability was noted. a marked lowering in stability was caused by the use of excessive amounts of alum. By careful control of the acidity of the stock in the beater, i.e., amount of alum added to the beater, it was possible to prepare well-sized papers of very high stability. Other factors being alike, papers with the lowest rosin content had the best resistance to accelerated aging.... When alum was used in moderate amounts as a preservative for the glue or starch in the surface-sizing baths, it caused no deleterious effect on the paper as far as could be determined by the tests applied (Rasch, Shaw, and Bicking 1931, 782).

In a 1933 NBS study, Kimberly and Emley found that chemical purity of the pulp was a major factor in permanence of paper. They studied the effect of the use of chemically impure pulps on permanence and predicted that book papers manufactured from 1875 to 1910 that contained fibers from groundwood and straw might be impermanent (Kimberly and Emley 1933).

In yet another summary, published as one of the NBS' miscellaneous reports in 1934, Kimberly and Scribner describe the findings of the series of NBS studies on paper permanence. However, this time they emphasized the 1933 findings of Kimberly and Emley, and left out much of the detail present in the other studies from NBS. Much of the emphasis in those other studies upon acid and alum rosin size as the principal cause of rapid paper deterioration was omitted, for example. They concluded, in a rather weak fashion, that the study of old papers showed crude fibers such as groundwood were in bad condition in contrast with papers composed of chemically purified fibers, which were generally in good condition (Kimberly and Scribner 1934). Knowledge of this article in isolation from the rest of the NBS's studies may have misled some persons to support the theory of fiber source as the major contributor to the rapid deterioration of modern paper.

In 1935, researchers at NBS published an article more clearly describing the relationship between acidity and fiber source:

Shaw, Bicking, and O'Leary studied rag-fiber papers and the factors which affect their stability. They found that high acidity resulting from excessive use of alum in rosin sizing has a marked deteriorating effect upon rag-fiber paper. and of rag papers of the same acidity, those having the lesser content of rosin were the more stable. They concluded that the initial quality of the fibers cannot be taken as a criterion of the degree of excellence of paper made from them. The study shows that careful processing of raw materials especially the control of active chemical components such as alum and rosin is necessary for the manufacture of stable papers. (Shaw, Bicking, and O'Leary 1935, 650)

In 1937, Kimberly and Scribner again reported the findings of the series of NBS research studies including those of old papers. They repeated their findings that regardless of fiber source, wood or rag, those papers having the highest alpha-cellulose contents were the most permanent, those with the highest amounts of both alum and rosin showed the most deterioration (Kimberly and Scribner 1937).

NBS's studies continued to support findings from the earlier German and Swedish research. for example, Scribner reported deterioration of very durable kraft paper was due to degraded cellulose that he attributed to acid hydrolysis caused by excessive bleaching. He measured deterioration in this study by loss of folding endurance (Scribner 1938). in the same year, Shaw and O'Leary found that the cellulose deterioration increased as the amount of alum was increased in both un-sized and rosin-sized papers. They concluded that acidity was therefore an important factor in deterioration (Shaw and O'Leary 1938).

During the 1930s Barrow corresponded with and visited Scribner regularly. Scribner was Barrow's tutor; he taught and guided Barrow in basic paper chemistry, research procedures, and lamination (see Chapters 8 and 9).

The Government Printing Office

The Government Printing Office (GPO) did not have the same national service goals to meet the technical information needs of the business community as did NBS, although it did freely share its knowledge. in 1922, George M. Carter, Public Printer, established the Technical Division to test printing supplies and materials including paper for compliance with specifications. "Over the years, the [Technical Division of GPO] . . . has been responsible for many new developments. Its research accomplishments . . . have aided the whole printing industry . . ." (Kling 1970, 40-74).

The Technical Division performed its compliance function, prepared new specifications for procurement of materials best suited to the requirements of the various processes and techniques used by the GPO, and engaged in "a modest amount of research . . . mainly in solving technical problems as they relate to specific printing jobs." the Paper Branch was the largest of the Technical Division's four branches (Kling 1970, 71). Morris S. Kantrowitz was a chemist employed by GPO in the Technical Division's Paper Branch. He was among Barrow's sources of expert knowledge of paper chemistry. His annotated bibliography became a basic resource in the technical literature in paper permanence and durability (Kantrowitz, Spencer, and Simmons 1940). He sent Barrow a copy as soon as it was published in 1940, and it helped to introduce Barrow to the German and, more importantly, to the Swedish work in paper permanence (Kantrowitz 1940).

Research on External Causes of Paper Deterioration

To study the effects of climate, Chapman compared books in various regions of India and in England. He reported in 1919 and again in 1920 that books in tropical climates deteriorated more quickly than did those in cooler areas of India and in England. Both high temperatures and high relative humidity contributed to increased rates of paper deterioration through increased rates of chemical deterioration and by creation of hospitable conditions conducive to the growth of mold and insect infestation (Chapman 1919, 301 and Chapman 1920, 223).

Much research was done on the effects of air pollution on the longevity of paper. Air pollution due to sulfur compounds from un-vented gas space heaters and gaslights was a major problem in cities during the late 1800s contemporary with the general recognition of rapid paper deterioration in the libraries and archives of these same cities. "Since sulfur exists as an impurity in most sources of natural gas, there was a steady supply of sulfur dioxide. This was oxidized to sulfur trioxide by metallic impurities in the paper, such as manganese and iron. Sulfur trioxide combines easily with moisture to produce sulfuric acid (Shahani and Wilson 1987, 243). Sulfuric acid is highly destructive to organic substances including paper.

Environmental studies were also part of the research series carried out by the NBS, and these showed major effects on paper deterioration from air pollution. Books stored in rural areas in clean air were compared with books from urban, polluted areas. The results were consistent and indicated the deteriorative effects of the acids deposited on paper from the polluted air (Kimberly and Emley 1933). These observational studies were supported by laboratory research that showed paper exposed to sulfur dioxide and nitrogen oxides, the most studied air pollutants, underwent substantial deterioration even if the pollutants were present in very small amounts (Kimberly and Scribner 1934). The importance of air pollution compared to residual acidity in paper from its manufacture continues to be an active area in permanence research (Porck, van Heijst, Smit, and van Leeuwen 1988).

Chemical Findings Reported in Library and Archives Literature

The NBS carried out its research series in paper permanence in part at the request of the American Library Association and the National Association of Book Publishers (Scribner, "Report of Bureau of Standards research on preservation of records" 1931, 409). As early as 1931, an NBS study by John O. Burton supported the fact that cellulose fiber source was not a major factor in permanence, but that the process of paper manufacture was. Permanence was negatively affected by acidity, with the highest levels of acidity being consistent with the highest levels of alum rosin sizing. Burton even anticipates the work Barrow did to develop modern methods of manufacture for permanent/durable paper with CLR's support in the early 1960s by asserting that it is possible to produce modern paper with both high printing and permanence qualities if librarians, manufacturers, and publishers cooperate (Burton 1931, 430-439). Although the research series, described earlier in this chapter, was undertaken explicitly to answer the questions of librarians and archivists, the series' results apparently had little impact on this audience.

The literature from archives and libraries shows little progression or incorporation of the findings from contemporary chemical research on acids, residual from the use of alum rosin size, as the major cause of paper deterioration. Instead, this literature repeats one known cause, poor environmental conditions of storage, especially exposure to the gaseous sulfur compounds emitted by combustion of gas, oil, and coal. The literature also asserted the inferiority of wood as a source of fiber and the superiority of cotton fiber paper regardless of its acid content.

In 1930 James Strachan, paper chemist and spokesman for British paper manufacturers, summarized the existing conflicts between librarians and papermakers in England. He emphasized librarians' ignorance of paper chemistry. Strachan pointed out that librarians did not understand the technical meanings of the terms they used such as "durability" and "permanence." Librarians, in their ignorance, condemned all paper made from wood because of the poor quality of groundwood paper. Also, their ideas about paper were out of date and unsupported by scientific evidence (Strachan 1930). This picture of librarians in England matched the evidence from the United States. Higginbotham found that as far back as 1900 librarians in the United States lacked interest in paper research.

If the degree to which a topic is addressed in the professional press may be taken as a fair measure of interest, we may infer that despite progress in research and thinking about paper, turn-of-the-century librarians remained largely concerned with the book's binding rather than the pages that binding sheltered. Indeed, members of the library community were followers, not leaders, in paper research, and seemed more troubled by modern book papers' lack of durability than by their impermanence. for many, a certain degree of mystery and misconception still surrounded the deterioration of papers, and few understood that processing short cuts and remnants of injurious chemicals were chiefly responsible for their weakness. (Higginbotham 1990, 150)

There was also an apparent lack of awareness about paper permanence research among librarians and archivists, even among restorers, well into this century. This lack of awareness was not caused by a lack of information available to the library and archives fields as can be seen by an examination of articles on paper permanence indexed in Library Literature, an index of articles by and of interest to librarians and archivists. It began publication in 1933 as a continuation of the earlier indexes, Bibliography of Library Economy, 1876 to 1920 (Cannons 1927), Library Literature, 1921- 1932, Supplement, and Causes and Prevention of Deterioration in Book Materials (Walton 1929). These indexes show that all of the work on permanence and durability done at the NBS was indexed, including for example, Scribner's 1931 "Report of NBS Research" (Library Literature, 1921-1932, Supplement 1934, 267). Also indexed were the influential 1925 article by Köhler and Hall (Walton 1927, 18) and Hall's 1926 article that foreshadowed all the permanence research findings of the NBS during the 1930s (Walton 1927, 19). Appendix 4 is a year by year analysis of the publication of chemical information as it appears in the literature of libraries. This comparison includes articles on paper permanence and durability published in the indexed literature of paper chemistry, library and archives literature, and those of Barrow. It ranges from 1867 (beginning date of indexing in library literature) until 1967 (the year of Barrow's death). Appendix 4 reveals many articles on permanence in the chemical literature and fewer, although most of the important and influential articles, in library and archives literature. These articles were available in the literature well before Barrow began publishing.

Some in the library field were familiar with this literature (Walton 1927 and Lydenberg and Archer 1931, 77). What was known about use of chemicals in restoration in the 1930s and 1940s centered around their use in stain removal and bleaching of foxing stains. Lydenberg and Archer in their classic work on book and paper repair mention one chemical study (Kimberly and Scribner 1934), in the context of the effects of air pollution of paper deterioration (Lydenberg and Archer 1945, 21). Acid is mentioned in Lydenberg and Archer, but mainly in conjunction with foxing, the reddish brown staining that develops on paper.

The foxed areas are more acid than the unfoxed or clean parts. Paper-infesting fungi can produce acid in a medium in which cellulose is the sole source of carbon for this acid by-product. Starch sizing increases acid, casein decreases it, rosin seems to inhibit both the growth of fungi and the production of acid. . . .
Paper weakened by improper methods of manufacture, by excessive variations in moisture, by unintelligent use tends to be favorable to growth of foxing....(Lydenberg and Archer 1945, 64)

Lydenberg and Archer then quote an Iiams and Beckwith article on the use of bleaching agents: Agents "may tend to impair the already none-too-stable paper, and should be restricted to extreme cases, and then applied only by experts. We have still to find a method of removing foxing from book that is at once efficient and yet shows promise of producing no deleterious effects in years to come on the paper treated." [(Iiams and Beckwith 1935, 236)] (Lydenberg and Archer 1945, 63-64)

Mention is also made that once bleaching is done, the paper must be well rinsed and neutralized. Although bleaching is discouraged due to the difficulty of properly balancing acids and bases, no mention is made of how to measure or mix the proper solutions to be used. Further, Lydenberg and Archer discourage the entire practice of bleaching and stain removal due to the toll it takes on the paper.

Dangers of weakening. Bear in mind also that this attack by chemicals, this washing and rewashing, this bleaching and tinting may be safe with paper of undoubted strength, but it is weakening even for the best, and certainly is dangerous for stocks with fibres affected by attacks of one kind or another. the experienced eye will decide not infrequently that it will be more satisfactory to accept the sheet with the stain and with a known and certain strength rather than to succeed in removing the stain and at the same time secure dangerous weakening of the fibres. (Lydenberg and Archer 1945, 68-69)

The chemical literature existed, was indexed, and was used by some librarians before Barrow had published anything or when he had published only very little. Appendix 4 reveals that Barrow learned of paper permanence contemporaneously with the availability of that knowledge to any librarian or archivist who was able or worked to understand and assimilate it as Barrow himself had done. Information on the complex nature of paper and its deterioration was available to librarians and archivists in the 1930s; the NBS disseminated it in non-technical language (Scribner, 1931), but librarians and archivists apparently did not heed it.

In her study of preservation in turn of the century libraries, Higginbotham gives a reasonable explanation for librarians' ignorance of paper that may still hold true for librarians today.

Despite the nascent interest in the preservation of paper – the very marrow of the book – the greater part of the period's research and activity focussed on external preservation approaches rather than the problems inherent in the materials of which books were made. This is not to say that librarians were unconcerned about deteriorating bindings and book papers, but that they devoted less energy to these topics; when they did address them, they only infrequently did so in terms of 'inherent vice'....Perhaps librarians chose to concentrate on external matters (library buildings, book stacks and book supports, book construction) because these were easily grasped and fully understood. While paper deterioration was a problem whose solution was basic to the success of all other preservation techniques, its enormity and mystery may have combined to confound librarians, leading them to address topics whose dimensions they could more easily control. (Higginbotham 1990, 178)

Neutralization of Acid Paper by the Addition of Alkaline Substances

Literature in paper chemistry had numerous nonspecific references that paper could be made more permanent by the addition of alkaline substances before and even after sheet formation. Specific reference to alkalization came from Edwin Sutermeister, a paper chemist employed by S. D. Warren Company in Massachusetts. He suggested that a paper formulated for stability should contain alkaline fillers. According to Shahani and Wilson, "Alkaline-filled papers made under Sutermeister's direction in 1901 remain in excellent condition today" (Shahani and Wilson 1987, 242).

High acid paper can be neutralized by the addition of alkaline substances after manufacture. Klemm, in a 1932 article summarizing early German work on permanence and durability of paper, stated that acidity can be avoided even in rosin-sized paper when the excess alum necessary to precipitate the size can afterwards be neutralized (Klemm 1932). The 1938 article by the NBS's Shaw and O'Leary concluded that paper with an excess of alum was highly acidic and unstable. Paper with an excess of rosin, which had a pH close to 7 or neutral, was considerably more stable than other alum-rosin sized papers. Paper samples containing calcium carbonate, an alkaline filler, showed an even better retention of their physical properties after accelerated aging (Shaw and O'Leary 1938).

Chemists in Germany and Sweden in the 1920s found that acidic paper could be neutralized and even made alkaline after manufacture (Klemm 1932). in 1936 a Canadian Chemist, Otto Schierholtz, patented a process for the chemical stabilization of paper using a water bath of alkaline earth metals, one of which is calcium carbonate (Schierholtz 1936). He was interested in preventing paper from tarnishing metallic paints, but his process had wider application in restoration (see Chapter 10).

By the end of the 1930s, the dynamics of paper aging and deterioration due to acid hydrolysis and the ameliorating effects of alkalization were well known and well documented. Shahani and Wilson summarize what was known then and what is still current information on paper deterioration.

Whether a sheet of paper lasts indefinitely or only briefly depends on the materials and methods used in its manufacture as well as on the environment in which it is stored . . . it has been repeatedly demonstrated that additives which create acidity within paper hasten its deterioration. Acidic species catalyze hydrolytic degradation of the polymeric cellulose molecules, reducing their chain length; even a few chain scissions per molecule cause a substantial loss of physical properties. Mildly basic species such as calcium or magnesium carbonate minimize the acid concentration and therefore the rate of the acid hydrolysis reaction. The cellulose molecule can also suffer hydrolytic cleavage in an alkaline environment. Hence the need for a weakly basic compound to buffer the pH of paper close to neutrality. (Shahani and Wilson 1987, 244-245)

Paper Permanence and the Causes of Paper Deterioration in Common Knowledge by the 1930s

The dynamics of rapid paper deterioration were so well known by the early 1930s that articles summarizing the current paper permanence research were appearing in general interest magazines. in a 1932 issue of Nature appeared a popular summary of the information from of paper permanence research. This summary contained all the necessary elements, although the facts presented were not entirely correct:

Prior to 1860, rags (that is, cotton, flax, and hemp) were the usual raw materials, and although excessive loading, bleaching, or alum may shorten the life of rag papers, they are generally recognized as being the most permanent. . . .
. . . it has been shown that the method of manufacture of the paper and the conditions of storage are equal in importance to the nature of the fiber in determining how long the paper will last . . .
Not only have opinions been expressed as to storage conditions, but in addition, . . . all agree that the . . . rosin content, and acidity . . . should be as low as possible....there is no evidence that papers made from esparto or chemical wood deteriorate if stored under proper conditions. at the same time, new, clean, white or unbleached rags are preferable for the best papers....(Deterioration of paper on aging 1932, 320)

Barrow's collected papers contain Kantrowitz, Spencer, and Simmons' bibliography and many citations, lists, and copies of articles in paper chemistry, including all the publications of the NBS on paper permanence and the 1926 article by Gösta Hall.

Barrow and the Swedish Model

The information on paper chemistry and paper permanence that Barrow learned from the chemists at NBS and GPO was based on the Swedish Model. the model emphasized acidity, introduced primarily by the sulfuric acid in alum rosin size, as the dominant cause of rapid deterioration of modern paper. Other, lesser causes include lignin (groundwood), bleaches, fiber source, and acids from air pollution. Useful tests of paper condition are acidity (pH) and folding endurance. New papers should be neutral or alkaline in pH, and should contain an alkaline buffer. Acid paper is always unstable, and will become steadily more acid over time. a useful test of aging characteristics, called accelerated aging, is dry-oven heating for 72 hours at 100° C (Conroy 1991, 2-3).

The Swedish Model was developed to conceptualize the making of new and permanent paper; that is, paper made from purified fibers (Conroy 1991, 3-4 and Conroy 1992). When Barrow applied these concepts to preserving old papers that are much more varied and complex than new permanent papers, he oversimplified the paper chemistry involved. The Swedish Model underestimated the role of lignin in paper deterioration because it was constructed on the study of new paper made from purified fibers that contain little or no lignin. Barrow underestimated the role of lignin in his own work by directly applying treatments suitable for new permanent paper to all papers including the aged paper of the Virginia county records and to newsprint, with its high lignin content. The steps in the development of Barrow's restoration system and the effects of some of his applications and overgeneralizations of the Swedish Model are detailed in Chapters 8, 9, and 10.

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