Long before TAPPI established its present Paper Permanence Committee, it had a Permanence and Durability Committee, which flourished between 1929 and 1938. The Committee's work is recorded in four known reports, two of which were excerpted in the November issue. They pointed out that the paper industry was responding to libraries' and other institutions' demand for permanence, and that they hoped to clarify the issues in the ongoing rag vs. wood controversy; they reviewed basic concepts in permanence and durability; described tests used for estimating probable life of paper; briefly reviewed the, history of I>ermanence research since 1890; described the role of storage conditions; surveyed the research literature of the last two years; and summarized factors affecting permanence. To ensure permanence, the Committee recommended "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."
Most of the third report is reprinted here, to make it more accessible to readers interested in the history of permanence research. None of the reports in the series should be taken as proof either that (a) everything was already known by 1935, or that (b) little of value was known.
This report was originally presented at the annual meeting of the Technical Association of the Pulp and Paper Industry, New York, N.Y., February 1935, and was published as "Permanence and Durability Committee Report" in Technical Association Papers 18, 470-472, June 1935. The Committee at that time was composed of F.C. Clark, Chairman; M.S. Kantrowitz, H.U. Kiely, J.L. Parsons, E.O. Reed, E. Sutermeister and B.L. Wehmhoff.
In the 1933 report (1) of the Committee on Permanence and Durability were gathered together such facts relating to the permanence and durability properties of paper upon which there was unanimous agreement among the members of the Committee. Recent literature on the subject was also critically reviewed by the Committee and its opinion was presented with respect to future work in this field.
The present report (unanimously adopted) aims to set forth those facts relating to the permanence and durability of paper which have been brought out in the light of more recent investigations, with especial reference to book papers. No critical review of recent literature has been made but a bibliography of bibliographies on the subject is appended, covering the period 1900-1933, inclusive. A list of literature references for the year 1934 is also included.
During the past year the Committee on Permanence and Durability has spent considerable time in revising for its approval a chapter entitled "A Study of Paper Permanence," soon to appear in the book "Methods for Reproducing Research Materials," by R.C, Binkley, Chairman of the joint Committee on Materials for Research of the American Council of Learned Societies and the Social Science Research Council. The technical information relating to permanence and durability in the chapter has received the unanimous approval of the Committee on Permanence and Durability. Portions of this chapter form the basis of the present report of the Committee.
The outstanding qualities required of a book paper are finish color, formation, opacity, ink receptivity, strength, cleanliness, and permanence and durability. Other qualities of a greater or lesser importance are feel, aesthetic value, etc., depending on the purpose for which the paper is to be used. The printability, opacity, cleanliness, color and strength qualities of book paper can be determined by suitable testing instruments and expressed in numerical terms. The other outstanding quality, namely, permanence and durability, is not as easily expressed. Permanence of a paper has been defined as the degree of resistance towards the degrading chemical action of the impurities in the paper or of materials in the surrounding air. Durability is the degree to which the paper retains its original qualities under usage. In a 1933 report from the National Bureau of Standards covering "A Study of the Deterioration of Book Papers in Libraries," by Arthur E. Kimberly and Adelaide L. Emley (2), it was brought out that important factors in the permanence and durability of book papers are (1) the chemical purity of the fibers in the sheet, and (2) the conditions under which the books are kept. Paper from books stored in urban institutions is uniformly more deteriorated than that from identical volumes kept in rural libraries, according to the Bureau of Standards investigation. The much thumbed over books in the children's department of the public library show the results of wear in use, but there is little doubt that the lasting quality of paper is not only dependent upon its environment but is partly related to the paper itself. This permanence quality, however, is not immediately apparent to the observer. The only absolute test of permanence and durability would require that one should wait to see what happens to the paper in the course of several centuries.
In the days when paper was an innovation in Europe, competing with parchment, it was regarded as dangerously impermanent, and there was legislation to prohibit its use in legal documents. Of the books printed in the earlier centuries enough have endured the effect of time to establish beyond question the permanence possibilities in papers made of the materials then in use. During the period 1875-1910, unpurified or crude fibers, such as groundwood, were frequently used in book papers. The National Bureau of Standards, in the report to which reference has already been made, found that book papers containing appreciable quantities of crude fibers were invariably in poorer condition than those containing rag and chemical wood fibers. The period, 1875-1910, therefore, is defined as one in which the paper in books published during this time may be quite impermanent. This serves to emphasize the importance of the chemical purity of the fibers themselves as a factor in the permanence of paper. At the beginning of the present century paper technicians were calling attention to the danger of printing on paper containing crude fibers, such as groundwood pulp. The conclusion was drawn at that time that papers had a life expectancy proportionate to the amount of rag stock used in their manufacture.
The distributing trade has little knowledge concerning the problem of paper permanence and durability. The market designations of paper ordinarily in use include size, weight, color, surfaced finish and a description of the raw material from which the paper is made. The raw material may be described with varying degrees of precision. The simplest distinction is that which runs between "rag" and "wood pulp" papers, and those which contain different proportions of both. The rags, however, are not of equal quality. The higher classes of rags require less Chemical treatment for paper stock and, therefore, yield a more permanent paper when carefully processed. The lower classes of rags usually undergo a more drastic chemical treatment before being converted to paper and do not yield as strong or as permanent a paper although for many purposes it may possess other more desirable properties. The wood used in paper making is also subject to various classifications: there is the distinction between the soft (coniferous) woods and the hard (deciduous) woods. Then there are different processes by which the wood is converted into pulp to receive consideration. First, there is the important distinction between "mechanical wood pulp" ("groundwood") and "chemical wood pulp." Newsprint paper, for instance, is chiefly mechanical wood pulp; most book paper is made of chemical wood pulp. By different kinds of chemical treatment the impurities in the wood are removed and a fiber of relatively high purity, compared to a mechanical wood pulp fiber, is obtained. Recently certain additional processes giving further purification to chemical wood pulps have appeared.
Within the past decade or so some paper users have become dissatisfied with the more or less crude paper specifications and have begun to introduce laboratory procedures in standardizing their paper purchases. The distributing trade has not followed this line of development, however; its interests have been heavily vested in the existing trade practices. Recently some of the larger users of papers, who could establish direct contact with the manufacturers, began to demand and to receive "specification papers." It is reported that about one per cent of the finer paper trade in 1928 was on a laboratory specification basis, and that by 1933 this had risen to ten per cent.
The specifications which were most successfully established were those relating to the physical strength qualities of the paper. Standard physical tests were tearing resistance, bursting strength, tensile strength and folding endurance. Government specifications for permanent all rag content papers have carried requirements as to the grade of new rag permitted for nearly ten years. In addition, limits as to rosin size and acidity have also been included. Specifications relating to probable longevity of a paper were not so easily set up but progress is being made in that direction.
The librarians seem to have been the ones who showed the first and greatest desire for permanence in book papers, but they were in a bad strategic position for making their desires effective. They were many times removed from the paper manufacturers; they have little influence on the publishers and none on the paper distributors. The Library Association set up a committee which drew up some permanence specifications for paper. In general, however, the paper trade continued to sell its goods as "100 per cent rag" "50 per cent rag" or "sulphite" and induced the buyer to believe that the mote he paid, the greater was the probable longevity of the paper.
When paper technologists began to work on paper specifications not only was the source of the fiber studied but its chemical and physical qualities were examined. In all paper' cellulose is the basic ingredient, although there is a difference in the structure of different fibers and this is an important characteristic in paper making. Furthermore, associated with cellulose in the crude or unpurified fiber there are often undesirable substances, called impurities, which are removed by chemical treatment as already indicated. These impurities vary in nature and in amount depending on the source of the fiber.
Tests which are often used to determine the purity and quality of a paper are acidity, sizing, alpha cellulose and copper number. In general there is agreement among paper technologists that the acidity and the rosin sizing should be kept low for a permanent paper. The alpha cellulose content of a paper refers to that portion of the cellulose which is not soluble in a solution of sodium hydroxide under certain defined conditions. These are entirely empirical conditions, however. The alkali-resistant or alpha cellulose content of the cellulose portion of a paper is presumably proportionate to the fiber purity, a high percentage alpha cellulose value being desirable for a permanent paper. The copper number is also indicative of fiber purity, the higher the number the greater the degree of fiber degradation. Other tests which have been used in specifying book papers for permanent records are: ash, folding endurance, bursting strength, and opacity. No single test can be considered at the present time as an adequate criterion of paper permanency. Even the list of tests, mentioned above, yield a not too satisfactory picture of the probable life expectancy of a paper as far as purity of the sheet is concerned. Other tests which may become more reliable indices of paper permanence are now in the process of development.
Paper manufactured from the highest grade of cotton rags, new whites, new cream and unbleached cotton cuttings, receives the minimum of treatment. The raw material itself is of a very high degree of purity and, carefully processed, yields from known experience a paper of very great permanence and durability. Such papers possess an alpha cellulose content over 95 per cent and a copper number considerably less than 1.0. Ordinary processes of making chemical wood pulp do not yield a product with 90 per cent alpha cellulose content. Purification processes are now available, however, whereby the alpha cellulose content of such pulps, referred to as purified wood pulps, approaches that of the medium grades of cotton rags. Purified chemical wood pulps have proven very satisfactory for certain papers and as a substitute for certain grades of rags. With our increasing knowledge of paper, its raw materials and manufacture, the future may provide a more permanent paper made from a greater variety of materials.
Several years ago Burton (3) proposed a set of specifications and a classification system for permanent book papers. In this system all papers are divided into four classes. The first class contains those papers which may be expected to have maximum longevity. A book paper fulfilling the requirements of this class would be particularly suitable for bound volumes of records having permanent value. The second class contains papers of high purity. Papers for semipermanent records and in fine editions of rare and costly books should fulfill the requirements of this class. The third class is composed of papers which, while not having as high a degree of purity as those in the first two classes, have a fair degree of purity. Such papers could be used where moderate longevity is desired, such as in reference periodicals. Papers in the fourth class are those suitable for current use only....
The interest of the paper trade in specifications is recent and welcome. Technical knowledge is far ahead of market conditions. Some of the conclusions of paper technologists are in satisfactory agreement and can be safely used as a guide by publishers in search of permanent paper.
A test made at the National Bureau of Standards confirms the fact that a purchaser who merely specifies a percentage of rag content in a book paper has no assurance that he is paying for permanence quality. Thus is the importance of careful specifications brought out.
In the previously mentioned investigation, carried out by Burton (3) at the National Bureau of Standards, the importance of the careful processing of fibers was emphatically brought out. A fiber of initial high quality may have its purity seriously lowered by improper processing and fibers of much lower original purity may be purified to a high degree by proper treatment. Ms results serve to bring out the importance of careful specifications in the matter of permanent and durable book papers, no single test or specification being adequate....
How are paper specifications to be interpreted? The paper technologist quickly draws the layman beyond his depth in the discussion, but a few facts stand out as agreed or uncontested, and upon these the publisher may safely base his policy.
1. Fiber Content of Highest Class Papers
It is always insufficient to specify merely a source of the fibers, as, for instance, "rag" or "50 per cent rag." Not only should the quality of the fiber be specified but specifications covering the manufactured paper should be carefully drawn. These should include ash content, acidity, rosin sizing, alpha cellulose, copper number, folding endurance, bursting strength, and perhaps other tests depending on the use requirements of the sheet. No one or two tests alone, anymore than the source of the fiber, can entirely define the permanence of a paper. For instance, some of the new fillers now being used in book papers will give a high false copper number without any other indication of impermanence. Others believe that a low alpha cellulose content of rags which have been properly purified is not an index of impermanence. It is natural that the more information we have concerning the properties of a rag paper, the more can we judge of its general quality and useability for the purpose we have in mind.
Although it is admitted there is no general agreement on the specifications necessary for a permanent paper made from fibers other than the highest grade of rags, the dealers and even the buying public in general have been slow to realize the need for and the significance of a permanent book paper. When the buyers specify these superior properties in a paper, the manufacturer will quote prices consistent with the specifications and the desired product will be delivered. It lies with the buying public to assist the manufacturers to keep pace with the findings of the paper technologists.
2. Fiber Content of Second Class Papers
Price becomes a leading consideration among the less permanent papers and specifications do not have to be as rigid as with the first class papers. Thus, in the Burton Classification for book papers of high purity for semi-permanent records the chemical and physical constants are extended considerably over those for book papers of maximum purity for permanent records. The buyer should test and carefully check to specifications all papers before use in order to be sure he is getting his full money value. Again, no single test should be used as a criterion of the permanence quality of the paper under consideration.
3. Ground or Mechanical Wood Pulp
No ground wood (mechanical wood) pulp or unbleached chemical pulp should be present in any paper designed for anything more than temporary use.
It is undisputed that high acidity causes rapid deterioration of paper. Acidity is measured in two ways: the acid number is determined by volumetric analysis and indicates the amount of acid present, while the pH value is a measure of the hydrogen-ion concentration or strength of the acid. A paper testing pH 4.5 for instance, is 32 times more acid than one testing pH 6.0 and is more likely to become degraded on this account.
5. Sizing Material
The presence of large amounts of rosin as a sizing material in paper is likely to bring about a discoloration or yellowing in papers on ageing. There is general agreement that the rosin content of permanent papers should be kept low.
6. Filler, or Loading Materials
There is not compete agreement as to the significance of mineral fillers for permanent and durable papers. Too much material will probably reduce the durability of the sheet but that a small amount of the proper filler does no harm is the opinion of many paper technologists.
As rag, purified chemical wood pulp or other papers at moderate prices prove to have satisfactory lasting qualities, the permanence level of all book papers can be raised, without greatly increasing prices. A basic economic argument helps at this point. The carefully manufactured rag papers with alpha cellulose content up to 97 per cent are probably more durable than a paper that merely passes the proposed Burton Class I tests. But it cannot be widely used in the publishing industry because of cost; its usefulness will lie in the small editions especially made for permanence, and the riskless editions which do not threaten to leave their makers with a great bulk of expensive paper unsold on the shelves. The improvement of permanence qualities in the normal product of the publishing trade must depend upon the development of less expensive papers. The buyer must be induced to demand what the technicians are able to make, a rag or purified chemical wood pulp paper manufactured for permanence, and sold at a moderate price....
(1) 1933 Permanence and Durability Committee Report.. Paper Trade J. 97, No. 4; 33-36 July 27,1933).
(2) National Bureau of Standards Miscellaneous Publication No.
140. (Obtainable from Superintendent of Documents, Washington, D.C. 5 cents.)
(3) Burton. Bureau Standards J. Research, 7, 429-439 (1931). Reprint Paper No. 349.
(1) Bibliography of paper deterioration, by H.M. Lydenberg. Paper 22, No. 19; 12-13 July 17,1918).
(2) Durability of paper (covering period 1900-Sept. 1928). "Bibliography of Pulp and Paper Making, 1900-1928," pages 272-278 (1929). Compiled by C. J. West. TAPPI.
(3) Durability of paper (1 928). 'Technical Association Papers," Series 12, page 155 (May 1929). Compiled by C. J. West.
(4) Durability of paper (1929). 'Technical Association Papers," Series 13, page 157 (May 1930). Compiled by C. J. West.
(5) Durability of paper (1930). 'Technical Association Papers," Series 14, pages 403-404 (May 1931). Compiled by C. J. West.
(6) Durability of paper (1931). "Bibliography of Paper Making1931," pages 33-34 (1932). Compiled by C. J. West. TAPPI.
(7) Durability of paper (1932). "Bibliography of Paper Making -1932," pages 33-34 (1933). Compiled by C. J. West. TAPPI.
(8) Permanence of paper (1933). "Bibliography of Paper Making -1933," pages 60-61 (1934). Compiled by C. J. West. TAPPI.
(9) The period Sept. 1930-Sept. 1934 is covered by volumes 1 to 4, inclusive, of the "Bulletin of the Institute of Paper Chemistry." Consult index to each volume under "Paper-Permanence."
Farquhar, S. T. Permanent paper in scholarly publishing. Paper Trade J. 98, No. 11; 22 (Mar. 15, 1934).
Grant, J. Some problems of fading. World's Paper Trade Rev. 100, No. 24; 1866,1904,1906 (Dec. 15, 1933); No. 25; 1944,1946,1984,1986, 1989 (Dec. 22,1933); Paper-Maker British Paper Trade J. 86, Annual Number 65-71 (1933). (This reference is included because it was omitted from most bibliographies for 1933.)
Richter, G. A. Accelerated aging tests for determining permanence of papers. Ind. Eng. Chem. 26,1154-1157 (Nov. 1934).
Scribner, B. W. Preservation of newspaper records. Paper Trade J. 99, No. 14; 31-M (Oct. 4,1934).
Strachan, J. Imperishable documents. Paper-Maker British Paper Trade J. 87, No. 1; TS 33-34 (Jan. 1, 1934).