Public interest in permanence was running high during the 1930s, and research on permanence was generously funded in both Europe and America, as if the Depression did not exist. TAPPI's Permanence and Durability Committee was part of that surge of interest. Its ten-year history, as reflected in the reports it made to the TAPPI Executive Committee between 1929 and 1938, was reviewed in the September issue.
The committee's mandate was to summarize the state of the art and to act as an advisory committee to TAPPI on the preservation as well as the manufacture of permanent and durable Paper, recommending directions for future research. It published four reports:
1. [Report published without a title, as part of an annual meeting report, Technical Association Papers 13 no. 1, 24-25, May 1930.
2. "Report of the Committee on Permanence and Durability of Paper," Paper Trade Journal 97 no. 4 (Technical Association Section), July 27,1933. Dual paging: 3740 (TAPPI Section) and 3336 (PTJ).
3. "Permanence and Durability Committee Report," Technical Association Papers 18,470-472, June 1935.
4. "Report of Permanence and Durability Committee," Paper Trade Journal 105 no. 9 (Technical Association Section), Aug. 26, 1937. Dual paging: 138-140 (TAPPI Section) and 42-44 (PTJ).
The first two reports will be excerpted here at length, with the permission of Pulp & Paper, the successor to the Paper Trade Journal.
... The paper industry during the past few years has given more and more attention to a study of manufacturing processes in attempting to produce papers of materially greater resistance to mechanical handling, usually called the durability of the paper.
Libraries and other institutions directly interested in the preservation of the written and printed record are demanding papers that will show the least possible deterioration with the passage of time, usually called the permanence of paper.
The first report of the committee is presented for the purpose of clarifying certain points. The first of these points is the definition of the terms permanence and durability. These terms are sometimes used interchangeably and sometimes with varying distinctions.
These two distinctions are most important and are, therefore, set forth as follows:
Permanence is the degree to which a paper resists chemical action which may result from impurities of the paper itself or agents from the surrounding air.
Durability is the degree to which paper retains its original qualities under continual use.
Papers deteriorate because of certain physical or chemical conditions or a combination of both physical and chemical conditions, thereby adding materially to the difficulty of arriving at a solution of the problem.
There are papers which are required for a high degree of durability but because of the peculiar usage, permanence over a long period of time is of secondary importance. This point is well illustrated in the case of our United States Currency. Paper deterioration from excessive handling is the largest factor in its ultimate life. Other papers requiring a high degree of permanence may be perfectly satisfactory and yet have a relatively low degree of durability. An example of this would be a book paper of the highest degree of permanence, in which case durability must be sacrificed in order to produce certain desired printing effects.
To date it is generally recognized that deterioration in paper is due to any one, or a combination, of the following conditions.
I. Mechanical handling.
II. Chemical changes caused by: a) Light either natural or artificial; b) Impurities in the paper; c) Substances in the air; d) Abnormal temperatures or humidities.
Deterioration due to mechanical handling may be indicated by the use of the regular physical testing equipment. Deterioration due to chemical change is a vastly more difficult problem because we know almost nothing about what these chemical changes are or about the influence of any of the four subdivisions noted above.
The problem of deterioration is a most difficult one and so complex that it may not be solved except by a long series of carefully controlled tests in which all of the known deteriorating influences are studied, first separately and then in combination, by those qualified to interpret the results.
Of the various tests advocated for estimating the probable life of a paper, no one test includes all of the factors of natural aging and therefore when used alone, leads to erroneous conclusions. Effort is now being made to develop such a combination of tests as will include all the factors of natural aging and will permit us to make a true estimate of the degree of permanence. At the present time it may be stated with absolute assurance that under present conditions no one is justified in drawing definite conclusions as to the probable life of a given paper.
Tests for alpha cellulose, copper number, cuprammonium viscosity, solubility in various chemicals, aging under sunlight and under ultra-violet lights, aging in ovens at various temperatures and aging in atmospheres containing various gases and many other tests are being used in paper testing. Many of these tests have been developed in the chemical cellulose industry such as in the manufacture of cellulose lacquers, gun cotton, artificial silks of various kinds, celluloid and other cellulose products. There are today also a number of well equipped paper laboratories both here and abroad that a-f e concentrating on the study of these problems.
In view of this interest it is believed that tangible results in the development of a satisfactory method for estimating the probable life of a paper may be expected in the near future.
... Much time during the past several years has been devoted by investigators both here and abroad to the study of causes affecting the permanence of paper, with conclusions attempting to point out remedial measures required by the paper manufacturer. Various experimenters have seriously disagreed with each other. Manufacturers of wood pulp papers and manufacturers of rag pulp papers have entered into controversies as to the permanence of their respective products. All of this has led to confusion, and a beclouding of the real issue, without benefit to the paper industry. Your committee deplores this condition and states without fear of contradiction that all branches of the paper industry will most assuredly benefit from a true knowledge and understanding of the subject.
Your committee includes in its report a review and criticism of some recent investigations which have appeared in the literature, chiefly during the past two years....
... The earliest recorded research concerning paper deterioration was conducted by the German Government about 1890 at Charlottenburg. Several years later, in 1898, the Royal Society of Arts in London presented an important report entitled, "The Deterioration of Paper." Both of these investigations presented similar findings, namely, that the most permanent " of paper should be made of cotton fibers. In 1904, the U.S. Department of Agriculture authorized a similar investigation and in 1911 a report was adopted which included a specification for a permanent printing paper. This specification is based not only on the fiber composition of paper but also on its other physical and chemical properties as well. Since that date the U.S. Government has purchased all its paper under technical specifications covering both physical and chemical characteristics of each kind of paper.
It has been recognized for some time that the quality of paper alone is not the sole factor in determining its permanence. The conditions under which the paper is stored are of equal importance. Even the most carefully manufactured paper from the best of raw materials may deteriorate more rapidly under poor storage conditions than paper made even of mechanical wood pulp under very good storage conditions. The importance of adequate storage conditions for the preservation of the written or printed record can not be too strongly emphasized. A recent publication* of the U.S. Bureau of Standards should be in the hands of all those interested in the preservation of records and is recommended by the committee. Evidence is available that illumination, for instance, of the space for storage files should be by the use of incandescent electric light bulbs, gas jets and direct sunlight should be excluded. It has been further pointed out that the storage space should be well ventilated with clean, dust-free air, washed to remove traces of acid, at reasonably constant temperature and humidity. It is recognized today that even groundwood book papers carefully made, protected and stored under adequate conditions, may have their useful life appreciably lengthened beyond what is usually considered the life of such papers.
The comparative stability of fibrous materials and the question of paper permanence have also been the subjects of numerous recent investigations. The following articles, published during the past two years in this country, on the subject of permanence and durability, are listed together with important deductions made and conclusions reached by the respective investigators. The committee has also included its comments as found necessary.
[References for nine articles published in 1931 or 1932, with commentaries by the committee, are given. Not all of them need to be summarized here, because several appear to have been selected only to bolster the committee's position that the validity of the accelerated aging test had not yet been demonstrated. -Ed.]
Durability of Purified Wood Fibers. G. A. Richter, Ind. Eng. Chem.,23,371-370[sic](1931) ...No great reliance can be placed on accelerated aging tests as being a true measure of the permanence of paper. A study of the changes produced in paper by the application of heat may serve a very useful purpose, however, in understanding certain relationships among the various substances comprising a sheet of paper. For instance, the presence of acid residues is [word missing: likely? known?] to cause hydrolysis of the cellulose and the effect of such substances can be intensified by heat treatment of the paper. In this article the statement is made that the deterioration of paper may be attributed mostly to oxidation and hydrolysis. Results of the investigation show that papers that are most resistant to oxidation and physical injury are consistently high in alpha cellulose content. The deleterious effect produced on papers exposed to sulphur dioxide gases was also observed.
The Permanence of Paper. B. L. Wehmhoff. Paper Trade Journal, TAPPI Section, pages 300-302 (June 9,1932). This article comprises an excellent review of the subject and is recommended by the committee to those interested in such a survey. In it, reference is made to the conclusions drawn by Dr. Herzberg of the German Materialprüfungsamt in 1908 based on an examination of 435 samples of paper intended for permanent records and submitted by the University of Berlin. Dr. Herzberg concludes that fiber composition alone is not a sufficient specification and that the quality of the raw materials and their treatment in the process of manufacture are important and can only be insured by strength specifications. The statement is made that the League of Nations have considered the subject of paper permanence and its committee of experts has made the following statement with reference to the composition of permanent papers:
"A preference at the present state of the manufacturing process to be given to unbleached rag paper; it being understood that new processes of treating cellulose may in the future provide paper of lasting quality."
... The committee is in agreement with the statement....
The Relative Stabilities of Rag and Purified Sulphite Pulps. H. F. Lewis. Paper Trade Journ., TAPPI Section, pages 239-262 (Nov. 24,1932). The investigation comprises a study of the chemical stability of three rag stocks and two purified sulphite pulps towards a variety of degradation agencies. These agencies included the use of heat under different conditions, alkaline solutions under varied conditions, acid solutions, and light from two sources.... The degradation was followed by the determination of such chemical constants as alpha cellulose, copper number, beta and gamma cellulose, pentosans, and cuprammonium viscosity.
Chemical stability is related, according to the author, to the alpha cellulose content of a pulp. High alpha cellulose content usually connotes a low copper number and such stocks are more resistant to the degrading action of the reagents investigated....
The committee believes that evidence is available to show that among the factors which are responsible for deterioration in paper are the following:
1) Mechanical treatment, such as the flexing of the fibers, and a roughening of the paper surfaces. This may result in a reasonable decrease in its physical properties, but without any necessary change in its chemical properties.
2) Chemical changes, resulting from light, either natural or artificial; impurities in the paper; substances in the air; and abnormal temperatures or humidities.
... All permanent paper specifications indicate the maximum amount of rosin permitted. Recent researches have shown that light and impurities in the rosin may have a bearing on t deterioration of paper.
The committee is of the opinion that future studies should deal with the different variables involved in the conversion of fibrous cellulosic material to paper; that a knowledge of these factors, such as beating, sizing, drying and finishing as well as the purity of the components of paper, and their relations, would place the industry on a much more scientific basis....
A study involving the storing of a variety of papers of known history under various known conditions for different lengths of time is recommended. At intervals of three to five years samples could be collected and tested independently by several paper technologists to be selected perhaps by the association.
... Time has proven that permanence is insured by the use of new white or unbleached cotton, flax or hemp fibers, carefully processed, in the manufacture of a paper which is stored under average conditions. This is due to the fact that the introduction of other cellulosic material, such as wood fibers, is rather recent. A well made modem chemical wood pulp paper will probably have a longer life than a similar paper made 40 years ago, although the precise life of a sheet is unknown.
Although the committee obviously tried to be objective, it seems to have overlooked the research connecting deterioration with low pH. Three of the nine publications cited in the 1933 report emphasized that acid was a major cause of deterioration, and one drew attention to the fact that pH fell as aging proceeded; but the committee toned down the authors' statements or ignored them. For instance, a Jarrell, Hawkins and Veitch paper on "The Effect of Inorganic Acids on the Physical Properties of Waterleaf Rag Bond Paper" states (according to the IPC Permanence Bibliography abstract) that "Small quantities of hydrochloric acid, sulphuric acid, or aluminum sulphate in the paper cause its rapid deterioration." The sentence the committee chose to quote was "Acids and acid salts exert a slow deteriorating effect on paper, which may not be observable for many years."
On the other hand, this inattention to research on the role of pH could have been due to prudence rather than bias or carelessness. The committee chairman was rebuked by the Executive Committee in 1933 for corresponding with "a certain purchasing organization" about the "probable life of paper of various compositions." Permanence specifications must have been a sensitive issue in TAPPI, probably because of the desire to avoid offending members whose papers might suffer by comparison.
At the time, very few people besides Warren's Edwin Sutermeister were advocating alkaline paper. (By 1932, Sutermeister was a member of the committee, though his influence was not apparent.) Even the Bureau of Standards, in its 1930 set of specifications for "absolutely permanent paper," set a minimum pH of only 5.0.
One's first impression, on reading these reports based on the research of 60 years ago, is that nothing has changed. One is surprised that they knew so much in those days. (We have to remember that researchers in every age have stood on the shoulders of giants.) However, there has been progress and technological change since 1933, a lot of it. The most obvious change has been the acceptance of higher pH as a factor in permanence, and the greatly increased availability of alkaline paper.
Testing and measurement have been revolutionized. Accelerated aging has been compared to natural aging in several studies, and a reasonable correlation found. The probable life of paper is no longer estimated by copper number or percent alpha pulp, but by pH, alkaline earth filler, and lignin content. Degree of polymerization or hot-alkali-solubility was used then, and is still popular. Several measures of the rate of deterioration of paper have been devised, but have not come into wide use yet, including thermoluminescence (investigated at the Battelle Institute in the U.S.) and the Russell effect, used at the British Library to detect oxidation over the surface of a paper or artifact.
In the 1930s, deterioration was tracked by measuring chemical changes after aging; today such testing relies heavily on various physical tests (fold, tear, and so on).
Word usage has changed too, becoming more specific. What researchers of the 1930s called "fiber impurity" probably referred most of the time to lignin, a term which is not mentioned once in these reports. They might also have been using the ten-n to include hemicelluloses, iron, or other substances.
The last two reports of the committee will be presented in a future issue of this newsletter.
* A Survey of Storage Conditions in Libraries Relative to the Preservation of Records. By A. E. Kimberly and J. F. G. Hicks. Bureau of Standards Miscellaneous Publication No. 128.