U.S. DEPARTMENT OF COMMERCE

DANIEL C. ROPER, Secretary BUREAU OF STANDARDS

LYMAN J. BRIGGS, Director

BUREAU OF STANDARDS MISCELLANEOUS PUBLICATION No. 144 SUMMARY REPORT OF

BUREAU OF STANDARDS RESEARCH

ON PRESERVATION OF RECORDS

By

A. E. KIMBERLY

B. W. SCRIBNER

Issued May 9, 1934

UNITED STATES

GOVERNMENT PRINTING OFFICE

WASHINGTON : 1934

For sale by the Superintendent of Documents, Washington, D.C. - - - - Price 5 cents

SUMMARY REPORT OF BUREAU OF STANDARDS

RESEARCH ON PRESERVATION OF RECORDS

By A. E. Kimberly and B. W. Scribner

ABSTRACT

The results of systematic studies, extending over a period of 4 years, of the

problem of preserving valuable records are summarized to have the more

important information available in one publication. Most of it was previously

reported in more complete detail in several publications.

A survey of material stored in libraries and of the conditions surrounding it showed that many valuable publications were badly deteriorated. Light, adverse temperature and humidity, acidic pollution of the air, and low-grade paper

were indicated as the main deteriorative agents. Through exposures of papers

to sulphur-dioxide gas, with measurement of the weakening effect, and the test- ing of papers from old books that had been stored in various localities, this product of combustion was proved a potential destroyer of all classes of papers. Experimental tests in a library demonstrated that this acidic gas can be completely removed by washing the air with alkaline wash water. The destructive

effect of light is emphasized by data showing its rapid weakening effect on all grades of papers. In discussion of the ventilation of libraries, the removal of dust and the maintenance of a medium degree of temperature and humidity are recommended. Carefully controlled air conditioning is desirable. Extensive

tests of old newspapers and books showed the deteriorative effect of crude fibers

,

such as ground wood; as papers containing them were generally in bad condition

as contrasted with the generally good condition of papers composed of chemically

purified fibers. A classification of book papers for record use has been suggested.

An outline is given of information developed elsewhere on protection against

insects, including the "bookworm", which is particularly difficult of extermination. Study of protective coverings for papers indicated that both Japanese

tissue and transparent cellulose acetate sheeting are quite suitable. The ordi- nary acid types of writing inks having been found very deteriorative to paper, the

organic chemistry section of the Bureau developed an alkaline ink that is apparently harmless. Permanent photostat paper is recommended for reproducing

records of perpetual value. This series of investigations was made with the assistance of a fund granted

for the purpose by the Carnegie Foundation to the National Research Council. CONTENTS

Page

I. Introduction 2

II. Plan of research 3

III. Survey of storage conditions in libraries 4

IV. Effect of air polluted with sulphur dioxide 6

V. Effect of light 14

VI. Ventilation of libraries 16

VII. Quality of paper 18

VIII. Insects 21 IX. Protective coatings 22

X. Writing inks 24 XL Preservation by reproduction 25

XII. Recapitulation of recommended practices 26

1
2 Miscellaneous Publications, Bureau of Standards

I. INTRODUCTION

The librarian is the custodian of the records of the past upon which

the progress of the future must be founded. His responsibility is great. If some future generation finds that important records have

reverted to dust, the loss to civilization may be irreparable. The

proper discharge of this duty requires that he assume responsibility

for the physical quality of the documents which he takes into cus- tody, and that he store them under such conditions as to promote

maximum longevity. It is the plain duty of the public to see that

librarians are given adequate support and permitted sufficient

freedom of action to accomplish their task. Cheap paper has been a potent factor in the development of

civilization. It has made both learning and news cheaply and

universally available, and has therefore become an absolute necessity in our present scheme of existence. But the present generation

has learned that cheap paper is not a quality product. The demand

for low price has led to the introduction of new raw materials; the

demand for enormous quantities has prevented the use of great care

in manufacturing. There is a tremendous and vitally important

market for such paper, but we now know that this market does

not include the printing of records designed for the use of future

generations.

The continued concentration of our population in cities has produced a new problem for librarians to face. The urban atmosphere,

polluted by smoke from heating and power plants and exhaust gases

from automobiles, less exposed to the purifying action of sunlight,

overheated by multiple reflections from paved streets and brick

walks, is far different from the fresh pure air of the open country

which was our customary living environment a hundred years ago. The preceding generation did not consider these things. Many

important records were printed on impermanent paper and/or were

stored under such conditions that they are now no longer serviceable.

The League of Nations, through its international cooperation, found

the present situation serious. The American Library Association

decided to do something about it. Largely on the initiative of H. M. Lydenberg, of the New York Public Library, the Carnegie

Foundation was persuaded to finance the project. Funds were

deposited with the National Eesearch Council to support fellowships at the Bureau of Standards. These funds were supplemented

by others appropriated by the United States Congress.

Work started on August 26, 1929, under the auspices of the following advisory committee, which was appointed by the National

Kesearch Council, and of which the chairman of the Division of Chemistry and Chemical Technology of the Council was ex-officio chairman:

Helen U. Kiely, chief chemist, American Writing Paper Co., Inc., Holyoke, Mass. H. M. Lydenberg, assistant director, New York Public Library, New York, N.Y.

H. G. Knight, chief, Bureau of Chemistry and Soils, Washington, D.C. W. D. Harper, president, W. D. Harper, Inc., paper merchants, 225 Fourth

Avenue, New York, N.Y.

G. A. Richter, director of Paper Research, Brown Co. (pulp and paper manufacturers), Berlin, N.H.
Kimberlyl

Scribner J Preservation of Records 3

B. L. Wehmhoff, technical director, Government Printing Office, Washington, D.C.

R. E. Flynn, Union Guardian Trust Co., Detroit, Mich., chairman, Paper

Standardization Committee of National Association of Purchasing Agents.

A. M. Chase, Dodd Mead & Co., New York, N.Y., representing National Association of Book Publishers, 448-449 Fourth Avenue, New York, N.Y. M. Krimmel, assistant director of laboratories, Hammermill Paper Co., Erie, Pa. Hervey J. Skinner, president, Skinner and Sherman, 246 Stuart Street, Boston, Mass. Work was stopped by the exhaustion of available funds on July 26,

1933, but the committee is continuing in existence and the laboratory

is being maintained intact in the hope that some way may be found

to resume operations.

The results of the work as set forth in the following pages comprise

first a description of the situation as we find it today. This is based

upon a survey of the conditions in libraries, and an examination of

records therein. Attention is called to the obvious wisdom of select- ing a quality paper for the printing of permanent records. Storage

conditions are, or should be, under the control of the librarian, and

he is advised concerning those factors which may cause trouble and

what conditions should be maintained for the maximum longevity of

the records in his keeping.

The work is not completed. We should find out what to do with

records which have been printed on paper which we now know to be

unsatisfactory. Is there some ingredient which can be added to paper which will make it more resistant to adverse conditions?

(Something like the " antioxidants" recently developed by the rubber

industry?) The physical and chemical reactions which occur when

paper deteriorates must be ascertained, for the work cannot be considered complete until this fundamental information is made available.

The present paper is a summary. Different parts of the work were

covered in separate reports as completed, and are referred to in this

text. The research work was conducted in the Bureau paper section

under the direction, successively, of J. G. F. Hicks and A. E. Kimberly,

with the assistance of A. L. Emley, assistant chemist, and W. L. Holt and G. O. Stone, laboratory assistants.

II. PLAN OF RESEARCH

Definite data as to the optimum conditions of storage for paper

were found to be meager. In fact, perusal of the literature showed

that prior to the work herein reported, no systematic, organized

research to determine the causes of the deterioration of paper in

libraries and similar depositories, and to find means of minimizing or eliminating this deterioration had ever been reported. This dearth

of reliable information was most unfortunate as proper manipulation

of storage conditions is the only means of prolonging the useful life of books and manuscripts available to the librarian. The literature

did, however, record that certain agencies—namely, light, 1 2 3 4 5 acid

i Klemm, P., Papier Zt, vol. 27, pp. 961-963, 1902.

* Schwalbe, C, Wochbl, Papierfabr., vol. 38, p. 1472, 1907.

» Schoeller, Viktor, Wochbl., Papierfabr., vol. 43, p. 3222, 1912.

* Haas, P>., Papierfabr., vol. 12, pp. 891, 919, 1914.

* Hitchens, A. B., Paper, vol. 22, p. 11, 1928.
4 Miscellaneous Publications , Bureau of Standards

gases,

6 7 varying temperature and relative humidity,8 9 and various

pests, 10 11 12 13 14 such as insects, mice, molds, and fungus—have been

considered harmful to paper in the past, although definite data were

lacking. It was, therefore, necessary to formulate a plan of research

designed to define clearly the agents of deterioration due to storage

and to find means of minimizing or eliminating action of these agents on stored records.

The plan of research originally formulated, after an extensive

review of the literature to avoid duplication of work, included a survey of storage conditions in representative libraries throughout

the United States to determine the degree of protection afforded

books against the effects of each of these deteriorative agents, except

pests, upon paper. As the work progressed, new lines of attack

became obvious; and considerable information on the effect of adhesives and writing inks upon the permanence of paper, the feasibility

of preserving newsprint by the addition of protective coatings, and

the quality of paper has been developed.

III. SURVEY OF STORAGE CONDITIONS IN LIBRARIES

A survey of libraries was undertaken to ascertain the kind and

amount of equipment which librarians have available for the protection of the records in their charge, and to get information about the

visible effects of light, dust, dampness, and similar factors. Thirteen libraries were selected to give a fair representation of conditions throughout the United States, in both urban and rural localities. Eight of these were personally inspected; information from the

other five was obtained by correspondence.

Details of equipment are shown in table 1. An inspection of table 1 shows that of the 13 libraries listed only 4

possessed the equipment necessary for the removal of dust from the

incoming air of their ventilating systems. Oil filters were used in

3 of the 4 libraries attempting dust removal. The elimination of

dust from library air is very important, for dust particles, in addition to their abrasive action upon the paper and bindings of stored

material, act as nuclei for the condensation of acidic moisture. 15 Every library inspected attempted to reduce the amount of dust in

the stacks and on the books by systematic dusting. In several in- stances small hand vacuum cleaners were extensively used.

s Girard, A., Am. chim. phys., vol. 24, p. 337, 1881.

7 Aribert and Bouvier, La Papeterie, vol. 42, pp. 338, 386, 1920.

s Norris, J., Library J., vol. 38, p. 16, 1913.

9 Braums, O., Pulp and Paper Mag. Can., vol. 26, pp. 11, 165, 1928.

10 Houlbert, C, Les Insectes ennemis des Libres, Paris, 1907. " Scarone, Arturo, El libro y sus enimigos, Montevideo, 1917. » Reinich, W. P*., Am. Jour. Phar., vol. 83, p. 503, 1911. » Pierre, Compt. rend., vol. 164, p. 230, 1917. Galippe, V., Compt. rend., vol. 169, p. 814, 1919.

18 Monnett Osborn Smoke Abatement, U.S. Bureau of Mines Bulletin No. 273.
Kimberlyl Scribner J Preservation of Records

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6 Miscellaneous Publications, Bureau oj Standards

Six of the libraries possessed machinery for humidity control, but

in two cases the apparatus was not in use at all and in a third instance,

the plant was effective only in cool weather, because of the lack of a

refrigerator. An attempt was made, several years previously, to use the third-mentioned plant in the summer, but when the advent

of a spell of cooler weather precipitated the moisture from the air

in the stacks upon the books stored therein, resulting in extensive

damage from molding, the attempt was abandoned. All of the

equipment in full time use was of the water-curtain type with no means of regulating the temperature of the water save in one instance

where modern thermostatic control had just been installed. The

average library using average equipment could not control the

humidity of the air within its stacks very closely.

The situation regarding the protection of books from the action

of daylight was considerably better than that dealing with the other

phases of protection, for 10 of the 13 selected libraries minimized

the effect of the actinic rays of light by the total elimination of

windows in 3 cases, or by the use of thick glass in the remaining 7 examples. In only one instance was sunlight admitted freely to the

stacks and it may be noted that excessive deterioration was apparent

in this case. Book stacks, in general, were found to be lighted by

small, frosted incandescent bulbs which were switched on and off as

required. This is a very desirable practice. " Yellowing" was observed in hot, dry, and dusty places in the

path of direct sunlight. Books stored in diffused light seemed to be

little affected. "Brittling" was also observed under the same cir- cumstances.

Dusty papers were frequently observed to be discolored and quite

often brittle, but no general rule for the correlation of these facts

could be formulated.

No damp places were observed at the time of this survey but

several spots were pointed out as being damp at other seasons. In

these places, the papers examined seemed soft and "

fuzzy", bearing a white powder which could readily be brushed off. They also showed

brown splotches known as "foxing".

Apparently little difficulty was being experienced with pests, as

is to be expected with the precautions taken to insure cleanliness and

good ventilation.

For further details on this subject, reference may be made to the

preliminary report. (See reference 26, p. 7.)

IV. EFFECT OF AIR POLLUTED WITH SULPHUR DIOXIDE

The earliest known published record of deterioration by sulphur

dioxide is to be found in a lecture given in April 1843 by Michael

Faraday, who declared that the rapid decay of leather bindings and

leather upholstery in the Athenaeum Club of London was due to the

effects of heat and sulphur fumes emanating from the illuminating

gas used. He recommended more thorough ventilation by a system

of ducts leading the products of combustion from each burner to a

central chimney.

No information as to the effect of illuminating-gas fumes upon

paper was available until 1898, when the Committee of the Royal

Society of Arts on the Deterioration of Paper reported as follows:
Kimberly]

Scribner J Preservation of Records 7

" Actual disintegration has been found to occur in all grades of paper;

it is the result of chemical change of the fibers themselves, and in some cases could be traced to the effect of illuminating gas upon the

atmosphere of the rooms in which the books had been stored." 16 The deleterious effects of gas fumes upon paper were further emphasized by Veitch 17 and by Aribert and Bouvier,18 who recommended

the elimination of illuminating gas from libraries. With the almost universal use of electricity for artificial illumination, danger to books from gas fumes was thought to be ended,

although the appearance of articles describing the effects of smoke

on vegetation 19 and building materials 20 in industrial localities, as

well as the deleterious action of the sulphur dioxide present in the

fumes emanating from certain types of smelters 21 22 indicated that

atmospheric pollution was prevalent to a greater degree than had

been hitherto realized. In recent years many investigations to determine the extent of this nuisance as well as means of abating

it 23 24 25 have been conducted. A study of statistics from 15

American and European cities 26 showed the sulphur dioxide content

of city air to vary from 0.2 to 3 parts per 1,000,000 parts of air and

an annua] precipitation of sulphuric acid averaging from 11 to 190

tons per square mile. Additional evidence of the increasing pollution of modern urban atmospheres is given by an investigation by

the Bureau of Standards of the causes of " winter damage" or the

rotting of damp cotton fabric upon exposure to outside air experienced by laundries throughout New England.27 Atmospheric sulphur

dioxide, which is oxidized on the fabric to sulphuric acid, was found

to be the cause of this rotting. This action was accelerated by the

presence of minute quantities of iron or of chlorine bleaching residues

in the fabric.

Despite the great amount of evidence at hand to show the increasingly acidic nature of modern atmospheres, no information of the

effect on paper of concentrations of sulphur dioxide such as are commonly encountered in the air of cities was found in the literature.

However, consulatation with librarians in different localities indicated a belief that the paper of books stored in city institutions

deteriorated more rapidly than the paper of similar volumes kept in

country or suburban localities, even though the wear and tear incident to use was approximately the same for each depository.

In the light of even the meager data on air pollution already considered 28 the possibility that the greater deterioration of books stored

in cities might be due to the action of sulphur dioxide was too obvious

» Jour. Royal Soc. of Arts, vol. 46, pp. 597-601, 1898. " Veitch, F. P., U.S. Dept. Agriculture Yearbook, p. 261, 1908.

18 Aribert and Bouvier, The Diseases of Paper, La Papeterie, vol. 42, pp. 338, 386, 1920.

19 Clevinger, J. F., The Effect of Smoke on Vegetation, Mellon Institute Smoke Investigation Bulletin No. 7, 1913.

20 The Effect of Smoke on Building Materials, Mellon Institute Smoke Investigation Bulletin No. 6, 1913. « Holmes, J. A., Franklin, E. C, and Gould, R. A., Report of the Selby Smelter Commission, U.S. Bureau of Mines Bulletin No. 98, 1915.

22 Haywood, J. K., Jour. Am. Chem. Soc, vol. 29, p. 998, 1907.

23 Recent Progress in Smoke Abatement in Manchester, Mellon Institute Smoke Investigation Bulletin No. 10, 1922.

24 Meller, H. B., Mech. Engr., vol. 48, pp. 11a, 1275, 1926. " Burrell, B. A., Proc. Leeds Phil, and Lit. Soc, Sci, Sec, vol. 1, pt. 3, p. 116, 1926.

28 Kimberly, A. E., and Hicks, J. F. G., Jr., A Survey of Storage Conditions in Libraries Relative to the

Preservation of Records, B. S. Misc. Pub. No. 128, 1931.

27 Wilkie, John B., Laundry " Winter Damage", B. S. Jour. Research, vol. 6, p. 593, 1931.

28 See footnote 26, p.
8 Miscellaneous Publications, Bureau of Standards

to be passed over. It was therefore decided to formulate a research

program having as its objectives:

1. The determination of the effect of low concentrations of sulphur

dioxide, such as are commonly found in the air of large cities, upon

paper.

2. The comparison of the effect on similar books of storage in

polluted and unpolluted areas with particular reference to the action

of sulphur dioxide.

3. If sulphur dioxide is important as a deteriorant of paper, to

find means of eliminating it from the air of libraries. The first phase of this program was initiated by exposing a series

of commercial book and writing papers of various fiber compositions

to the action of a sulphur dioxide air mixture, in which the sulphur

dioxide content was maintained at 2 to 9 parts per 1,000,000 parts of

air. The exposure was carried out at 30 C (86 F) and 65 percent

relative humidity for 240 hours.

Twenty sheets (8 by 10% inches) of each paper to be exposed were

conditioned at 21 C (70 F), and 65 percent relative humidity for 48

hours, after which they were removed to the test cabinet where they were suspended and exposed for the required time. The cabinet,

illustrated in figures 1 and 2, was a double-walled box, fashioned of

sheet metal and glass, the inside dimensions of which were 18 by 30

by 20 inches. It was equipped with suitable apparatus for the

control of temperature, humidity and sulphur dioxide content, a

detailed description of which may be found in an earlier publication. 29 After 10 days' exposure the paper samples were washed with

nitrogen for 24 hours and then tested for folding endurance, acidity,

copper number, and alpha cellulose content. The procedures used

for the determination of alpha cellulose content and copper number

were developed by the Bureau of Standards specifically for testing

paper.30 The alpha cellulose content of paper is that part of the

cellulose material which is insoluble in a sodium hydroxide solution

of mercerizing strength (17.5 percent NaOH) under certain specified

conditions and is regarded as a measure of the amount of unmodified

cellulose which the material contains. A high alpha cellulose content is considered an indication of superior condition in paper. The

copper number, on the other hand, is a measure of the amount of

modified or deteriorated cellulose present and, when high, is regarded

as an indication of poor condition in paper. The acidity of the papers was determined by the fiber suspension method.31 The results of these tests show that in every case a decrease in

folding endurance and an increase in acidity occurred and that these

changes were usually of considerable magnitude. The increase in

acidity, while significant in any event, is more so if caused by sul- phuric acid formed by the oxidation of sulphur dioxide upon the paper.

There are good grounds for such an assumption since Wilkie 32 showed that such an oxidation takes place upon cotton fabric,

« Kimberly, Arthur E., Deteriorative Effect of Sulphur Dioxide Upon Paper in an Atmosphere of Constant Humidity and Temperature, B.S. Jour. Research, vol. 8, p. 159, 1932.

30 Burton, J. O., and Rasch, R. H., The Determination of the Alpha Cellulose Content and Copper

Number of Paper, B.S. Jour. Research, vol. 6, p. 603, 1931.

si See footnote 29.

3» See footnote 27, p. 7.
B.S. Miscellaneous Publication No. 144

Figure 2.

Rear view of apparatus for exposure of paper to sulphur dioxide showing

control accessories.

Kimberlyl

Scribner J Preservation of Records 9

especially in the presence of iron,33 34 36 and since both cotton fabric

and paper are essentially cellulose. The analogy is completed by

the fact that most papers contain small amounts of iron derived

from iron equipment, water, and reagents used in the paper-making

processes. Sulphuric acid, being nonvolatile at ordinary temperatures, would remain upon the paper and exert a continuous effect. Either sulphurous or sulphuric acid is capable of promoting acid

hydrolysis 36 which results in the embrittlement of paper fibers and

their eventual crumbling.

Further consideration of the data shows that exposure to sulphur

dioxide caused a distinct increase in copper number accompanied by

relatively small changes of the alpha cellulose content (that is, 8

out of 14 specimens show changes of 0.5 percent or less). This would

indicate that the first point of attack is that portion of the material

of the sheet which had originally been partially modified by " hydration" in the beaters or otherwise. The embrittlement shown by

decreased folding endurance is added evidence for this point of view,

as folding endurance is commonly considered to be partially dependent on the cementing action of the gel-like portion of the paper fiber. It is not known whether or not a longer exposure to the action of sulphur dioxide would result in more pronounced changes in alpha

cellulose content. On comparing the embrittlement of the papers with their qualities

for permanent record use as shown in other publications,37 38 it appears

that there exists no constant relation between their quality and

their resistance to sulphur dioxide. This is illustrated for the book

papers by a medium quality paper having an alpha cellulose content

of 83 percent and a copper number of 3.07 which failed completely

under the heat test,39 but showed practically no change upon exposure

to sulphur dioxide and a paper suitable for permanent record use, having an alpha cellulose content of 95 percent and a copper number

of 0.40, which withstood the heat test with very little change, but

lost about 30 percent of its folding endurance upon treatment with

sulphur dioxide. The writing papers examined show a similar tendency. For instance, one sample having an alpha cellulose content

of 78.9 percent and a copper number of 3.25 and another with an alpha

cellulose content of 78.5 percent and a copper number of 3.67, both

low grade papers, showed poor stability under the heat test, but were

relatively unaffected by sulphur dioxide, The opposite was true

of two permanent record papers having alpha cellulose content of

85.3 and 91 percent and copper numbers of 1.71 and 1.06, respectively.

These findings show that even the best grades of the papers ex- amined were not proof against the deteriorating action of air polluted

by sulphur dioxide, which is in accord with the findings of Richter.40

33 Cooke, S. F., Role of Certain Metallic Ions as Oxidation Catalysts, Jour. Biol. Chem., vol. 10, p. 289,

1926.

3* Wilson, L. P., Catalytic Action in the Oxidation of Cellulose, Jour. Soc. Chem. Ind., vol. 39, p. 177T,

1920.

35 Baudisch, O., and Davidson, D., Catalytic Oxidation by Means of Complex Iron Salts, Jour. Biol. Chem., vol. 11, p. 50, 1927.

36 Heuser, West and Esselen, Textbook of Cellulose Chemistry, p. 121, McGraw-Hill Book Co., 1926.

37 Burton, J. O., Permanence Studies of Current Book Papers, B. S. Jour. Research, vol.7, p.429,1931.

88 Rasch, R. H., A Study of Purified Wood Fibers as a Paper-Making Material, B. S. Jour. Research,

vol. 3, p. 469, 1929.

3» Rasch, R. H., Accelerated Aging Test for Paper, B. S. Jour. Research, vol. 7, p. 465, 1931. « Richter, G. A., Ind. Eng. Chem., vol. 23, no. 4, p. 371, 1931.
10 Miscellaneous Publications, Bureau of Standards

Table 2.

Effect of temperature and relative humidity on action of sulphur dioxide on paper 1

Paper no. Fiber composition Temperature Relative humidity

Decrease

in folding endurance 2

Increase

in acid- ity Rag Sulphite Soda

94001 book paper

Percent Percent

40

40

Percent

60 °C

3040

40

40

30

40

4040

30

4040

40

Percent

6540

6580

6540

6580

6540

6580

Percent

14

17

29

48

7

611

311422

26

90

Percent

38

64 126

189

10162

198 352

99 155

194

391

94008 bond paper.. 60

94011 bond paper 100

1 240 hours exposure to 2 to 9 parts sulphur dioxide per 1,000,000 parts of air.

2 Average of machine and cross direction. In order to determine the effect of temperature and relative humidity upon the deterioration of paper due to sulphur dioxide, several

selected specimens were exposed to the action of 2 to 9 parts sulphur

dioxide per 1,000,000 at 40 C and 40 percent, 65 percent, and 80

percent relative humidity, respectively, for 240 hours. Table 2 shows

the effect of such exposure upon three papers. It will be noted that

the degree of deterioration increases markedly as the temperature

and relative humidity are raised. These data are shown as they

have not previously been published.

However, regardless of the mechanism of the reaction, the mere

fact that sulphur dioxide in concentrations approaching those actually encountered in the air of cities may cause paper to deteriorate

markedly in so short a time as 10 days is an indication of the gravity

of the problem of paper preservation.

In view of the results of the work just described, it would not be

surprising if a book which had been exposed to an urban atmosphere,

polluted by sulphur dioxide, deteriorated to a greater extent than a

similar book stored in a country or suburban locality relatively free from air pollution. Accordingly, a group of 34 deteriorated books was obtained through the courtesy of the New York Public Library

and a list of these titles was sent to libraries throughout the United

States with the request that duplicates be forwarded for examination.

The libraries were further requested to submit for examination any

outstanding examples of paper, deterioration or preservation which

could be spared. By this means, 229 books published during the

period 1720 to 1930, as well as 85 duplicates of 31 different titles were collected from 23 libraries in widely separated localities. The similar books were carefully inspected to insure uniformity

of edition and date of printing, and the records of the contributing

institutions were checked so as to include for examination only those

books which had been subjected to approximately the same degree

of use while in circulation. This final process of selection yielded a group of 11 titles, each represented by two or more volumes. The

paper of these books was tested for alpha cellulose content, copper

number, acidity, and folding endurance, using the procedures previ-
Kimberly~l Scribner J Preservation of Records 11

ously discussed.41 The same portion of each different book was

tested to insure absolute similarity of sample.

A careful survey of the surroundings of each contributing institution was made in person or by correspondence when a personal investigation was impracticable, in order to determine whether the atmosphere

in the vicinity of the library was polluted or relatively free from acid

pollution. For example, the New York Public Library is situated in

the heart of New York City surrounded by high buildings, a condition

under which one might expect to encounter a marked degree of atmospheric pollution. Analyses of air in this locality show 0.8 to 1.2 parts sulphur dioxide per 1,000,000 parts of air.42 Similarly, the

University of Pennsylvania Library is located in down-town Philadelphia, bounded on one side by main line railroad tracks and in

close proximity to an oil refinery and numerous chemical plants .. The sulphur dioxide content of air in this vicinity was found to vary

from 0.1 to 1.8 parts sulphur dioxide per 1,000,000 43 parts of air

and damage to the foliage of elm trees in the University Botanical

Gardens has been observed by members of the university staff. With these highly polluted localities may be contrasted that of Iowa

State College situated several miles from the center of Ames, Iowa, in an area relatively free from industrial pollution.

It was found that the paper of books stored in libraries where the

atmosphere is characteristically urban (for example, New York Public

Library) contained more acid than other copies of the same books

kept in libraries where the atmosphere is less likely to be polluted

(for example, Iowa State College). This increased acidity was invariably accompanied by decreased strength and in most cases by an

increased copper number and a decreased alpha cellulose content, all of which are indications of poor condition in paper.

The principal difference between storage conditions in cities and

storage conditions elsewhere is the presence in urban air of measurable

quantities of sulphur dioxide. This gas, a product of the combustion

of fuel and of certain industrial processes, has already been shown

to be harmful to paper, and papers exposed to its action exhibit an abnormally high acidity. Comparison of the acid content of paper

after natural aging for 4 years in an atmosphere relatively free from

sulphur dioxide, and after exposure for 240 hours to the action of 2

to 9 parts sulphur dioxide per 1,000,000 showed that the acidity of

the specimen exposed to the action of sulphur dioxide was markedly

higher than that of the naturally aged specimen of the same paper.

Since it has already been shown that the acidity of books stored in

large cities, such as New York and Philadelphia, was usually considerably higher than that of similar books stored in country or suburban

libraries, and that sulphur dioxide, which in the process of acting on

paper produces high acidity in the paper, is present in the air of such

cities, it seems reasonable to ascribe the greater deterioration noted

in the books from city institutions largely to the action of sulphur

dioxide. (See reference 50, p. 20.)

Since it has been definitely established that sulphur dioxide is one

of the principal factors governing the deterioration of paper, the

necessity of providing protection for valuable books and records

against the action of this gas is very evident. The elimination of

*i See footnotes 29, 30, p. 8.

42 Communication from the Bell Telephone Laboratories.

43 Information from the University of Pennsylvania Botany Deparment.
12 Miscellaneous Publications, Bureau of Standards

sulphur dioxide by washing the library air was thought to be the most

feasible method as regulation of the temperature and relative humidity

of air in the storage spaces by means of air-conditioning systems is already accepted as the best practice. However, the efficiency of an

air-conditioning system of the conventional type with respect to the

removal of acid gases was not known. It, therefore, seemed desirable

to learn whether washing air in the customary manner completely removes sulphur dioxide and, if not, how the air-conditioning procedure can be modified to provide air for libraries that is completely

free from that harmful constituent.

The conduct of the work as planned required the use of a library

equipped with suitable air-conditioning machinery. The cooperation

of the Folger Shakespeare Library, Washington, D.C., in this respect was therefore secured as its facilities include an air-conditioning system

designed to provide the proper atmospheric temperature and humidity

wdthin the stacks and vaults. The Carrier Engineering Corporation,

makers of the air-conditioning machinery on which the tests were made, assisted through the services of an engineer as did the Metropolitan Refining Co., specialists in water treatment.

The sulphur-dioxide content of the air before and after washing was determined by a slight modification of the method of Griffin and

Skinner.44 A further discussion of the air-conditioning machinery

and of the method of analysis will be found in another report.45 The hydrogen-ion concentration of the wash water in the air-conditioning system was frequently determined colorimetrically in order

to find the relationship between the amount of sulphur dioxide in

washed air and the hydrogen-ion concentration of the wash water.

It had been previously suggested that the efficiency of existing air- conditioning systems with respect to removal of sulphur dioxide

might be increased by raising the alkalinity of the wash water.46 This was accomplished in the course of these experiments by adding

a mixture of certain alkaline salts at a rate sufficient to maintain the

hydrogen-ion concentration of the wash water within the range pH

8.0 to 9.0. This particular mixture of chemicals forms a passive

gelatinous deposit upon metal surfaces, thereby retarding corrosion

due to contact with water. In localities where a high degree of at- mospheric pollution is encountered, the metal parts of air-conditioning

systems corrode so rapidly, if preventive measures are not taken, that

complete replacement has in certain cases become necessary after less than a year of operation. The hydrogen-ion concentration of the

wash water in one system, where rapid deterioration was noted,

dropped from pH 7.4 to pH 6.0 in the course of 8 hours' operation,

because of the absorption of acid from the air washed. It is obvious

that protection against corrosion is necessary under such conditions.

Figure 3 gives the average results of the experimental work for each

day from January 6 to February 16, 1933. It compares the sulphur

dioxide of the untreated air entering the library with that of the

washed air inside, with reference to the effect of washing with untreated water and water treated with the alkaline mixture. Figure

3 also shows the three successive changes or different treatments of

the wash water, with the varying hydrogen-ion concentrations which

44 Griffin, S. W., and Skinner, W. W., Small Amounts of Sulphur Dioxide in the Atmosphere, Ind. Eng.

Chem., vol. 24, p. 862, 1932. « Kimberly, A. E., and Emley, A. L., A Study of the Removal of Sulphur Dioxide from Library Air, B.S. Misc. Pub. No. 142, 1933.

48 See footnote 26, p. 7.
Kimberly]

Scribner J Preservation of Records 13

characterized them. From January 6 to 24 the wash water was untreated and unchanged, though enough fresh water was continuously

added to make up for that lost by evaporation. During this period

the hydrogen-ion concentration of the wash water averaged pH 7. From January 25 to February 4 the water was treated with the alkaline mixture already described at such a rate that the hydrogen-ion

concentration of the resulting solution fell only momentarily below

pH 8.6. On February 6 the system was drained completely and

refilled with fresh, untreated water of pH 7.7. It is evident from figure 3 that air washed with untreated water in an air-conditioning system of the customary type, though containing

less sulphur dioxide than unwashed air, was still appreciably con-

.50

.45 O 40 o

o

o

O 36

S I CC

Hi .30

Q.

V)£.25

2

J .20 o

x2 .15 o

.10

—I3.05

.00

• INCOMING AIR UNTREATED TREATED

WASH WATER WASH WATER

pH 7. P H 8.4T0 9L2

WASHED AIR UNTREATED

WASH WATER1

,H 7.7

J 1 I 1 L -4-4

p H 8.0 /•A.M. FEB. I

JAN FEB DATE OF TESTS

Figure 3.

Comparison of the effect of washing with untreated and treated water on the sulphur dioxide content of library air. taminated. Figure 3 shows further that complete removal of sulphur

dioxide was effected by washing the air with treated water. Although

the sulphur dioxide content of the unwashed air varied from hour to hour and from day to day, the amount of sulphur dioxide present in

the air after washing apparently depends upon the hydrogen-ion concentration of the wash water. This relationship is illustrated in

figure 4. As the alkalinity of the wash water decreased because of

the absorption of sulphur dioxide coupled with insufficient additions

of the alkaline material, the sulphur dioxide content of the washed

air rose. Air treated with water having a hydrogen-ion concentration of pH 8.6 or above was completely free from sulphur dioxide

and, in that respect, suited to use in libraries. It is therefore recommended that libraries, particularly in localities where a high degree of atmospheric pollution is encountered, be
14 Miscellaneous Publications, Bureau of Standards

equipped with air washers; or better, complete air-conditioning sys- tems. To insure complete removal of sulphur dioxide from the air,

the water in the air washer should be changed at least once a week

and treated continuously with an alkaline solution so that the hydrogen-ion concentration of the wash water may always fall within the

range pH 8.5 to 9.0. All air returning from the storage spaces

should be rewashed to eliminate the chance of recirculating any sul- phur dioxide that might have leaked into the system. It is considered best to run the entire air-conditioning apparatus continuously.

V. EFFECT OF LIGHT

The discoloration ("yellowing") and eventual embrittlement of

newsprint or similar papers containing crude ground-wood fibers

pH OF WASH WATER

Figure 4.

Relationship of the sulphur dioxide content of washed air to the hydrogen-ion concentration of the wash water. when exposed to the action of light is a well known phenomenon and

most librarians take more or less adequate precautions to prevent its occurrence. However, it had been generally assumed that discoloration and embrittlement due to light always occurred together and

that absence of discoloration after prolonged exposure of paper to

light necessarily implied an absence of embrittlement as well. This

assumption probably accounts for the lack of protection against light

observed in some institutions handling high-grade papers only. No

information as to the effect of light upon the strength of papers free from crude fibers could be found in the literature. It, therefore,

appeared desirable to obtain information as to the effect of light on

papers made from all of the usual types of chemically purified fibers,

with respect to discoloration and weakening of the papers as well as about the role played by the various components of paper. For this

purpose test papers were made in the Bureau paper mill from com-
Kimberlyl

Scribner J Preservation of Records 15

mercial fibers under carefully controlled conditions. Unfortunately,

it has been possible to complete only tests of papers made from sul- phite wood fiber, and from a much purer wood fiber produced by

special chemical treatments. Specimens of these papers were subjected on each side to the action of light from a carbon-arc lamp for a period of 100 hours. The temperature of the test specimens was

kept below 40 C during the exposure by blowing air over them. The

cooling of test specimens during artificial light exposures is a neces- sary precaution that is often overlooked, as the high temperature of the lamp may affect the paper more than the fight does.

Table 3.

Effect of light on test papers

Fiber composition Sample no. Highly

purified wood

fibers Sulphite

Sizing Folding

endurance °

901 Percent Percent

100 None .„__..__ . Doublefolds 320 901-H72 " 150 901-L200 « 54 902 100 Rosin ... 180 902-H72 » 56 902-L200 • 23 909.„ ._ 100 None 3, 700

3, 200 440 909-H72 b 909-L200 • 910 100 Rosin 2, 500

1,600 300 910-H72 >> 910-L200

« For test specimen 90 by 15 mm. Average of machine and across machine directions.

*> Heated 72 hours at 100 C.

e Each side exposed to carbon-arc light for 100 hours. Table 3 contains data on the original folding endurance of one

unsized and one sized sample of each type of paper, as well as the

folding endurance of the same paper after light exposure and after

the heat test. The latter is a form of accelerated aging test that has

been extensively employed at the Bureau.47 It will be noted that the light exerted a marked deteriorative action

as shown by the greatly decreased strength of the specimens exposed

to the rays of the arc lamp. This was even true in the case of sample

909 which was quite stable under the heat test. Despite the extensive

weakening effect of the light, there was no apparent discoloration of the purer papers and the sulphite papers were only slightly discolored.

These data, although not extensive, show quite definitely that good

grades of record papers are susceptible to deterioration by light, and

that deterioration from this source may take place without visible

evidence. Rasch 48 also obtained data of this kind. He exposed a

series of papers consisting of 100 percent rag fiber, 100 percent sulphite

wood fiber, and mixtures of these fibers, representing the usual grades

of bond papers, to the action of direct sunlight. Each side of the

specimens was exposed for a period of 100 hours. This treatment,

47 See footnote 39, p. 9.

48 See footnote 39, p. 9. 36378—34 2
16 Miscellaneous Publications, Bureau of Standards

which was probably less severe than exposure to carbon-arc light,

produced losses in folding endurance of from 25 to 63 percent. No

observations of degree of discoloration were made.

Since perusal of the literature showed that the available knowledge

of the effect of light on rosin paper-sizing materials was extremely

contradictory, an investigation of the light sensitivity of these com- pounds was made.49 It was found that rosin, whether unbleached or

purified by bleaching, darkened considerably during exposure to

light, that the presence of oxygen was not necessary for this change

in color and that the darkening was accelerated and intensified by the

presence of ferrous iron. Ferrous resinate, a compound of ferrous

iron and rosin, was also shown to be sensitive to light.

As an extension of this work, papers contaminated with various

amounts of iron were made and tested for light sensitivity. The

presence of appreciable quantities of iron in the papers was found to increase markedly the degree of discoloration produced by exposure

to light. A tendency towards increased loss of strength in the case

of the specimens containing iron was observed, but no definite data

to this effect were obtained because of the extensive effect of light

upon the uncontaminated samples; see table 1. It is believed that a more precise study of the effect of light, particularly ultra-violet light, upon paper than was possible with the

equipment at hand would yield valuable information relative to the

preservation of records. Such a study should include an investigation

of the effect of monochromatic light of various wave lengths with a view to determining the exact frequencies responsible for paper

deterioration. Colored glass is sometimes used for the purpose of

filtering out actinic rays of light, but definite data on the efficacy of

this practice are lacking. In any case, direct daylight must be re- garded as a potential destroyer of all forms of record papers, and its use should be discouraged. If used, its effect should be minimized by

diffusion with suitable window glass or curtains over windows.

Indirect lighting by incandescent lamps and the use of lead-glass

bulbs for such lamps in direct lighting are preferable practices. In

storage stacks the lamps should be turned on only when actually

needed.

VI. VENTILATION OF LIBRARIES

Paper, cloth, thread, adhesives, and leather, the organic constitu- ents of books, are susceptible to decay from chemical changes brought

about by deteriorative components of the book materials, or by exterior influences such as sulphur dioxide in the air, and sunlight.

There is also the rotting effect of mildew which results from spores

carried by the air. All of these deteriorative actions are stimulated

by certain temperatures and humidities. The abrasive action of

dust has previously been mentioned.

Book paper saturated with water looses nearly all its strength;

but it is not conceivable that the paper in a book could ever pick up

this amount of water from the air. Perfectly dry paper is relatively

brittle. Prolonged exposure of a book to an atmosphere of less than

15 percent relative humidity might render the pages tender. Direct

or prolonged heating will also make paper brittle, so books should not

be placed near steam pipes or radiators.

*» Kimberly, Arthur E„ and Hicks, J. F. G., Light Sensitivity of Rosin Paper-Sizing Materials, B.S.

Jour. Research, vol. 6, p. 819, 1931.
Kimberty]

Scribner J Preservation of Records 17

The cloth and thread, whether of cotton or linen, are not materially affected by any extremes of humidity or temperature which

could normally be expected in a library. The thread in much-used

books sometimes gives way to a repeated stress well within its ulti- mate strength. The cloth may be sized with starch or similar water

soluble adhesive. This may become sticky if the humidity is too high, or brittle if it is too low, and is susceptible to attack by oxygen in

the presence of moisture and light.

Glue and casein are colloidal materials containing, normally, much

water. If the humidity gets too high (much above 70 percent) they

are likely to become sticky, which probably does no harm. But if the humidity drops much below 40 percent, glue which is stored in

contact with such an atmosphere for a considerable length of time

is apt to become so brittle that the sudden opening of the book will break it. Glue is permanently damaged by prolonged exposure to temperatures below freezing (25 F may be taken as the freezing point

of glue containing a little water)

.

Leather is not affected by temperature or humidity within the

ordinary ranges. The oils and greases which are worked into leather

to preserve its flexibility have a definite, though very low, vapor

pressure. They are gradually lost by evaporation and should be

replaced at intervals by rubbing the leather with neat's-foot or

similar oil. Mildew is a term popularly used to designate any one of a variety

of vegetable organisms. All of these have certain characteristics

in common: they propagate by means of spores, which are almost

always present in the air. They can remain dormant for an indefinite

period until the conditions become right for their growth. They

grow very slowly at low temperatures (40 F), very rapidly at the

optimum temperature (which differs with the species), and are

killed by high temperatures (some species as low as 100 F). The

different species subsist on different kinds of food; many kinds can

live on glue and starch, and at least one is capable of digesting the

pure cellulose found in cloth and paper. They all require an abundance of water. Unless the growth of mildew continues unchecked

for a considerable time, it is not likely to do any harm other than

create an unsightly appearance. If the relative humidity is kept

under 80 percent, paper, cotton, or leather will not contain sufficient

water to support the growth of mildew; glue and starch will. These

latter materials can be treated to prevent mildew growth, betanaphthol being generally used for this purpose.

Dust may be composed partly of the product of the slow growth

of mildew. It consists mostly, however, of small angular particles

of siliceous material. These particles are so small that they can become embedded between the fibers of the leather or the cloth, and

perhaps even of the paper. Subsequent flexing of the material may

cause the angular dust particles to cut the fibers. The danger of

damage from dust is so slight that it can be eliminated by a reasonable

amount of care. Deterioration caused by sulphur dioxide has already been discussed.

It is necessary to consider how the relative humidity in a building

varies from time to time. During the summer, if the building is neither heated nor cooled, the temperature and relative humidity

of the air inside the building and out of doors will on the average be
18 Miscellaneous Publications, Bureau of Standards

the same, and the relative humidity prevailing under these conditions

is in most cases not injurious to the books. It is true that if a period

of relatively cool weather is followed by a period of warm damp

weather, the warm nearly saturated air, coming in contact with the

cool books, may deposit moisture on them or increase the moisture

content to a point where mildew may develop. In winter the conditions are different. The outside air has a rather high relative

humidity, but being cold, its moisture content is small. When this

air is heated, its moisture content is not changed appreciably, but

while it is warm, its relative humidity is much lower than that of the

outside air, and as it passes over the books it dries them out in some

cases sufficiently to injure them. Hot air is not necessarily dry air, but if cold air is heated without adding moisture to it, its relative

humidity is decreased and it becomes "dry." To maintain a higher

relative humidity in a heated building in winter it is necessary to add

water vapor as the air is heated.

In general, then, the air in a heated building has a rather high

relative humidity in summer and a low relative humidity in winter, even though the relative humidity of the outside air may be nearly

the same in both cases. Consequently, during the winter the books

dry out, while in summer the moisture content increases in some cases

to an extent sufficient to cause injury.

In considering conditions of temperature and relative humidity

for the storage of records, economy of operating expense and comfort

of the personnel caring for the records must be considered as well as the preservation of the records, although this must be the determining

factor. It is, therefore, recommended that 70 F and 45 percent

relative humidity be maintained in storage spaces in the winter and

85 F and 45 percent relative humidity be maintained during the

summer months. It is felt that these conditions are satisfactory

for the preservation of records, and the higher temperature recom- mended for the summer months will result in lower operation costs

as well as lessen the shock to employees upon leaving or entering

the conditioned area. Under conditions such as these, the stored

material possesses good strength and flexibility, and the growth of

molds and fungi is minimized.

A positive circulation and diffusion of air through the library, or

at least the storage stacks, is desirable, in that it will facilitate proper

control of temperature and humidity conditions. It is necessary

to take in a supply of outside air only to meet the requirements of

the people in the library. Temperature, humidity, and chemical

condition of the air can be maintained at their optimum values (so

far as the books themselves are concerned) at lowest cost and with

greatest ease, by recirculation of the air within the building. Dust

should be removed from the air. VII. QUALITY OF PAPER

Although librarians are not responsible for the quality of papers in

publications given into their care, they can and have exerted considerable influence in raising the standards for such papers. They

are in an advantageous position to study the lasting qualities of the

papers, and their observations and reports of the presence of decaying

papers in all classes of printed matter have drawn attention to the

many cases of impermanent papers bearing records of perpetual value.
Kimberly~\

Scribner J Preservation of Records 19

This is more particularly true of papers made since the early part

of the nineteenth century, when the increasing demand for cheaper

papers resulted in efforts to find less expensive raw materials and

manufacturing processes, that gradually led to the development of the present practices. Prior to this time all classes of papers, even

newsprint, were generally made from cotton or linen rags, slowly

and carefully, entirely or largely by hand, and without much use of chemicals. Most of these papers have withstood the test of time.

The search for new fibrous materials brought straw into use by 1830,

chemical wood pulp produced by the caustic-soda process in the sixties,

and between this time and the eighties, the acid-sulphite chemical

wood pulp and ground wood pulp. While ground wood pulp furnished

the final solution for cheap printing paper, particularly newsprint, it has been an adverse factor in the preservation of printed material of

all kinds. Until the impermanent nature of this and other crude

fibers became known by experience with them, they were used in- discriminately in all classes of publications. Coincident with the

development of pulping processes for new kinds of fibers, came the use of inexpensive rosin sizing for paper and gradual development of the present machinery for mass production of pulp and paper in an

inexpensive way.

The present types of record papers have probably not been in

existence for more than 25 to 100 years. The time varies with the

kind of paper. This is insufficient time to determine whether any

of them will age as gracefully as the old hand-made papers. To

obtain information on the influence of different fibers on aging

qualities of papers, specimens of papers from over 300 old books and

newspapers were examined for state of preservation as related to the

kinds of fibers present. The specimens were considered to be in good

condition if there was little apparent weakening of the fibers and little or no discoloration. At the other extreme they were rated in bad

condition if they broke readily on creasing between the fingers and

were highly discolored. Paper that had apparently deteriorated

appreciably usually had a light to dark brown color. The newspaper specimens examined covered very thoroughly the

various transitions in paper-making practice outlined above, as it was possible to secure specimens from the files of libraries and publishers representative of newspapers published during the period

1830 to 1900, at approximately 5-year intervals. The specimens were from 24 eastern papers and 12 west-coast papers. The book papers

ranged over much the same period as the newspapers but the publication dates of the books were at irregular intervals as they were

secured more particularly for the study of effect of sulphur dioxide

described in section IV. The results of the fiber analyses of the old papers from the newspapers and books revealed practically identical usage in the past,

as far as time periods are concerned, of the various fibers that have

been used for such publications. Rag fibers were found exclusively

until 1868, when the first straw fibers were found, followed by ground

wood in 1869, and chemical wood in 1870. Rags are still commonly

used in the higher grades of book papers but in newspapers their use

is now confined to limited issues made for the permanent files of public

libraries. The latest newspaper composed, in part, of rag fibers was

dated 1895. From 1867 to 1895 the newspapers, and many of the book
20 Miscellaneous Publications, Bureau oj Standards

papers, were composed of various mixtures of rag, straw, chemical

wood, and ground wood fibers. Apparently the present newsprint

paper, composed of a mixture of chemical wood and ground wood

fibers, became well established by 1895. The latest newspaper containing straw was dated 1885. A few of both the book and the newsprint papers were found to be composed entirely of straw. Ground

wood was found in book papers extensively until 1904, but most of

the book paper now used is composed entirely of chemical wood fiber. The first of the latter type of paper was found in a book published

in 1889.

The comparison of the kinds of fibers found in the papers with the

condition of the specimens is striking evidence of the necessity of

avoiding low-grade fibers for records of permanent value. This is best illustrated by review of the results obtained with the newspaper

specimens, because they are more thoroughly representative of the

various fiber usages than are the book papers. All of the 36 newspapers composed of rag fibers, chemically treated, 57 to 103 years

old, were in good condition. Of 17 papers consisting of straw or mixtures of rag, straw, and wood fibers, 53 to 65 years old, 23 percent were in poor condition. Seven of these papers that were in good

condition were composed wholly or largely of straw or wood fibers,

showing that fibers from these sources may have good life if properly

purified. Contrasted with the generally good condition of the papers

containing only chemically purified fibers, of 51 papers containing

crude ground wood fibers mixed variously with rag, wood, and straw

fibers, 33 to 64 years old, 78 percent were in poor condition. Most of these deteriorated papers were so weakened that they would withstand very little handling. The book papers yielded the same findings

as the newspapers in respect of influence of purity of fibers on their

aging quality. In some of the old books good grades of paper were

found mixed with poor grades, which is one cause of uneven deterioration of different pages often observed in old books.

The foregoing quite definitely outlines periods during which publications, even most important ones, may contain impermanent papers

because of use of low-grade fibers in their manufacture. In the case

of book papers, as before mentioned, the use of ground wood fibers

for the important classes of publications was probably largely dis- continued about 1904. Because of the necessity for inexpensive paper,

the use of crude fibers in newsprint has continued. Fortunately, the

evident impermanence of modern newsprint led to the initiation in

1927, by the New York Times, of the printing of special library editions on high-grade paper, and this practice has since been followed

by several other newspaper publishers.

The complete report of this study of old book papers has been

published,50 and the details of the study of old newspapers will be the

subject of a future publication.

The Bureau of Standards, at the request of the American Library

Association and the National Association of Book Publishers, made

a study of the quality of the present commercial book papers, for the

purpose of assisting in the establishment of standards for such

papers, from the viewpoint of their use for records. The results

have been reported by Burton,51 of the Bureau staff.

»° Kimberly, A. E., and Emley, A. L., A Study of the Deterioration of Book Papers in Libraries, B.S. Misc. Pub. no. 140, 1933. « See footnote 37, p. 9.
Kimberlyl

Scribner J Preservation of Records 21

In this work 28 commercial papers, representative of the different

grades, were subjected to thorough tests for chemical purity, strength,

and stability. Their stability was measured by subjecting them to the accelerated aging test, previously mentioned, which consists in

exposure to air at a temperature of 100 C for 72 hours, and measuring

any changes in strength and chemical properties. While the validity

of this test as a measure of the relative resistance of papers to deterioration from internal causes is a debatable matter, the Bureau has

found that it agrees well with results of exposures to sunlight,62 exposures at more normal temperature and a 4-year period of natural

aging. As in the case of the old book papers studied, the more

stable papers were those containing the purer fibers, that is, fibers

high in alpha cellulose and low in copper number. Good quality

in this respect had no constant relation to the source of the fibers or their initial quality, which points to the necessity of careful processing of fibers, as well as careful selection of them, for the manufacture of stable papers. In many cases high acidity from the alum

used in rosin sizing the paper was apparently the cause of poor

stability. Rosin itself has been shown to be a potential promoter

of deterioration, and although the amounts found in these papers were not excessive, the Bureau stated that it was questionable if the use of rosin in book paper is necessary. On the other hand, clay

filler, the remaining principal component of book paper, was considered to have no harmful effect as it may be considered chemically

inert. From the above considerations a classification of book papers

based on fiber purity in terms of alpha cellulose and copper number,

a minimum of injurious chemicals, and strength, was suggested.

This comprises four grades ranging from paper for permanent records

to paper for records of current value.

The tests of the current book papers indicated that the quality of papers available for permanent records was not in general as good

as considered desirable, and this was attributed to the probability

of good printing quality having been given more attention than per- manence. The situation in this respect has no doubt been materially

improved by the constantly increasing cooperation between paper

manufacturers, printers, and librarians.

VIII. INSECTS

The protection of stored records from the depredations of insects

is one of the most serious and difficult problems of the librarian.

Constant warfare must be waged against this form of destruction.

Climatic conditions render this problem more or less acute in differ- ent localities, but no library is free from it. The cellulose in paper

and fabric attracts certain species of insects and some kinds are more

particularly fond of other book components, such as glue, starch or

casein.

The more or less common pests, the termites or white ants, the

various species of cockroaches, and the silverfish, are destroyers of printed material, and methods of poisoning or trapping them are

well known. Advice as to extermination of specific insects of this

kind can be obtained from the Bureau of Entomology, United States

Department of Agriculture, Washington, D.C.

« See footnote 39, p. 9.
22 Miscellaneous Publications, Bureau of Standards

Some protection against insects is secured by the use of poisonous

or repellent materials incorporated in bindings and in varnishes and

lacquers used to coat books. In extreme cases fumigation is resorted

to. Hydrocyanic acid, sulphur, formaldehyde, and carbon disulphide are some of the more common fumigants used. In both of these practices, care should be taken that the substance used is harmless to paper and binding materials. Sulphur fumes are known to be

deteriorative. Of the fumigants mentioned, carbon disulphide, if chemically pure, is probably the safest, but in any case the stored

material should be carefully aired after fumigation to minimize the

possibility of injury. The California Institute of Technology in

cooperation with the Huntington Library, San Marino, Calif., has

developed a new fumigant, which is a mixture of ethylene oxide and

carbon dioxide. The commercial preparation is termed "carboxide."

This is said to be harmless, effective, and neither explosive nor

inflammable.

The Huntington Library has made considerable study 53 of the

ehmination of the so-called " bookworms" (Sitodrepo panicea) which

are particularly harmful and very difficult to combat. The insect

that causes the bookworm trouble is commonly known as the drugstore beetle.54 The beetle itself is a voracious eater of nearly all kinds of materials, and it has the further bad habit of depositing its eggs near the surface of book bindings or on the edge of the leaves.

As soon as the larvae are hatched, they eat their way to the interior of the book, then again to the surface when ready for the chrysalis stage,

and a full-grown beetle finally emerges. According to the report of

the Huntington Library, the only way to completely exterminate

this pest is to kill the larvae by forcing poisonous gas into their

tunnels in the books. They found that vacuum treatment was

necessary for killing both larvae and eggs . The fumigant 1

' carboxide '

is used in a large vacuum chamber, specially designed for the purpose,

which accommodates several trucks of books at one time.

Further references to information on this subject will be found in

the general review of literature in section II. Librarians are cautioned that hydrocyanic acid, formaldehyde,

and carbon disulphide are extremely poisonous to human beings, and

are quite inflammable. Fumigation with such substances should be

conducted only by an expert.

IX. PROTECTIVE COATINGS

Librarians and others desirous of preserving newsprint and other

similarly short-lived papers are confronted with the necessity of

treating the paper in such a manner as to render it more resistant to handling and to retard the processes of deterioration as much as

possible. The mode of treatment must be reasonably low in cost,

simple and easy of application. In addition to being more stable, it

is desirable that the paper after treatment shall not be inordinately

increased in bulk and weight. Increased bulk is particularly to be

avoided as storage space for newspapers is usually at a premium in

the average library.

« Iiams, Thomas M., The Library Quarterly, vol. 2, No. 4, p. 375, 1932. m Howard, L. O. and Marlett, O. L., The Principal Household Insects of the United States, Washington, D.C., 1896. See also footnote 10, p. 4.
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Scribner J Preservation of Records 23

In general, two methods of applying protective coatings have been

used, namely, building up a film upon the surface of the paper sheet

by dipping it into or spraying upon it a solution of a cellulose ester such as cellulose nitrate or cellulose acetate or by causing a previously

formed film to adhere to the paper with or without an adhesive.

Results obtained by treating paper with solutions of cellulose esters have not generally proved satisfactory, from the standpoint of either

service or economy.

The application of Japanese tissue, a thin, tough tissue paper of high chemical purity, has been extensively practiced, using a mixture

of rice starch and tapioca destrin as an adhesive. This material,

which may be applied by hand or with the aid of apparatus designed

for the purpose by the New York Public Library, increased the

strength of newsprint very greatly. Paper treated in this manner

also resisted the effects of the heat test satisfactorily. The tissue

itself showed practically no change after subjection to the accelerated

aging procedure. However, this method of treatment was found to be disadvantageous in that the weight of treated paper was almost

double the original weight while the bulk was trebled, which is undesirable. Moreover, the ease with which the contents of the

newspaper were read was considerably diminished because of the

semitransparent nature of the tissue paper.

It was thought that this last difficulty could be removed by substituting transparent viscose cellulose sheets for the Japanese tissue. This substitution proved to be unsatisfactory since the cellulose sheeting itself exhibited unsatisfactory permanence qualities as shown by the fact that its alpha cellulose content was found to be

only 77.4 percent, and was decreased to 72.6 percent by heating at 100 C for 72 hours.

The recent development of cellulose acetate foil, 0.001 inch thick,

led to the trial of this material as a preservative for newsprint.

Since cellulose acetate is thermoplastic (i.e., flows under the influence

of heat and pressure), it was easily applied to the newsprint by placing a sheet of newsprint between two slightly larger sheets of cellulose acetate foil and transferring this combination to a hydraulic press where, under the action of heat and pressure, one homogeneous unit was obtained. Newsprint treated in this manner was found to be

very stable to the heat test and to the action of light from a carbon

arc. Moreover, no impairment of legibility was caused, nor was

there an objectionable increase in bulk as the thickness of newsprint was increased only 0.0005 inch by this treatment. However, the

weight of a specimen of newsprint protected by cellulose acetate foil (0.001 inch thick) was found to be approximately two and one half

times that of a similar unprotected specimen. Other workers engaged

in similar researches abroad concur in these findings.

Cellulose nitrate sheetings, which include celluloid, are relatively

unstable and may have a deteriorative effect on papers brought in

contact with them.

The New York Public Library has reported 55 the results of trials of a wide variety of protective materials, including chiffon, silk, cellulose lacquers, varnish, and Japanese tissue paper. They considered the

last named the most suitable of those tried.

Lydenberg, Harry M., Preservation of Modern Newspaper Files Library J., vol. 40, p. 240, 1915.
24 Miscellaneous Publications, Bureau of Standards

X. WRITING INKS

That writing inks may be deteriorative to paper is well known, as instances have been observed where the ink has eaten its way through

the paper of old documents. Moreover, as the usual type of writing

ink is acid, it would be expected to adversely affect paper. While

considerable study of this subject has been reported by Herzberg 56 and others, their findings have been rather contradictory in respect

to the component or components of the inks that may cause deterioration of paper. Their tests were made on papers that may have been

somewhat different from the present domestic papers, and little attention was given to the proportion of ink and paper. In view of

these considerations, further study of the subject seemed desirable,

particularly as the organic chemistry section of the Bureau desired

to include study of this kind in a general investigation of properties of

writing inks.

For the study, seven writing papers were selected which were representative of the commercial range of fibers, and of the sizing materials

usually present in such papers. The organic chemistry section prepared the various inks used for experimentation, and inked the test specimens of papers. The ink lines were drawn across one half of

the sheets of paper with a drawing pen, of such width and spacing as to simulate the proportion of ink and paper of the average written

document. The inked specimens were then subjected to the heat

test, and the relative retention of folding endurance of the inked and

uninked portions of the papers was determined. The inks used were

the usual iron-tannic acid-hydrochloric acid type, one of which was

prepared according to the U.S. Government specification 57 for writing

ink, and the other the same except that sulphuric acid was used instead

of hydrochloric. Lines were also drawn with the components of the

Government standard writing ink in various mixtures or used separately, in solutions of the same concentration as in the ink.

It was found that all of the papers were appreciably weakened by

the accelerated action of these inks. The inked portions of the

papers lost from 13 to 50 percent more of their initial folding endur- ance than the uninked portions. With respect to the different components, solutions containing, respectively, hydrochloric acid, ferrous

sulphate, gallic acid, tannic acid, and a mixture of hydrochloric acid

and ferrous sulphate, produced losses in folding endurance of about

the same magnitude as the ink itself. The other components had

relatively little effect. In view of these findings E. W. Zimmerman, of the organic chemistry section, prepared inks of various formulas, until finally an ink was found that caused practically no loss of folding endurance of

papers inked with it. This ink was prepared with ammonium-oxyferri-gallate according to the method of Silbermann and Ozorovitz.68 The solution used had the same concentration as that of the standard

Government writing ink. The writing qualities of this ink were

satisfactory as was its lack of sedimentation on standing. While some further study of its use is desirable, it appears to offer considerable promise for use in documents that are to be retained a great

number of years.

«6 Herzberg, W., Papierfabr., vol. 54, no. 2, p. 104, 1923. w Federal Specification TT-I-563, Dec. 9, 1930.

a* Silbermann and Ozorovitz, Bull. soc. stiinte Bucuresti, vol. 17, p. 43, 1908; Chem. Abstr., vol. 2, p. 2685, 1908; Chem Zentr., 1908, ii, p. 1024.
fr?6S

y

] Preservation of Records 25

XL PRESERVATION BY REPRODUCTION

In order to conserve space and for other reasons many libraries

have adopted the practice of photographing rare or perishable material upon small sections of motion-picture films known as film slides. In this manner it is possible to condense considerable material into a very small space (a standard newspaper sheet may be contained in a section of film approximately 1 by 1.25 inches), and when needed

for reference, the slide may be projected through a stereopticon

upon a screen, thus rendering the printed matter easily legible. As a means of avoiding wear and tear upon valuable manuscripts, and of providing wider circulation for rare books, this method of reproduction

is admirable. From the standpoint of the preservation of records,

however, it is doubtful if any great increase in permanence of the

records would result from the copying of manuscripts or similar

material from impermanent paper upon photographic film. Photographic film consists of an emulsion containing the light sensitive

material bound usually in gelatine, and a base of cellulose nitrate or

cellulose acetate upon which the emulsion is spread. After exposure

the film is chemically treated to render the emulsion insensitive to further exposure to light. As a result of this chemical treatment,

small quantities of reagents are left upon the surface and in time

cause deterioration of the emulsion, and this results in a gradual

diminishing and eventual total extinction of the image. This occurs even through the most careful treatment is accorded the negative.

Moreover, the base of the film is exceedingly sensitive to the effects of light, variation in humidity, and temperature. Each of these

agents produces an embrittlement of the base and tends to decrease

the bond between the base and the emulsion of the film. Cellulose

nitrate films decompose under the influence of mild heat and humidity

with the liberation of oxides of nitrogen which attack the emulsion.

Cellulose acetate or safety film, on the other hand, is more apt to become brittle and shrink through storage in too dry an atmosphere

than are other types of film. Ideal conditions of storage for safety

film are 50 F and high relative humidity approaching saturation. 59 These conditions are difficult and uneconomical to maintain throughout the year, but if adhered to, the safety film should last for a considerable period of years. It therefore appears that more permanent

reproductions may be obtained by the use of photostats than by the use of film slides or similar methods. Photostat prints are stable

and do not fade if they are properly fixed and washed, and are printed on stable paper. The Bureau of Standards has made extensive

tests of photostat printing papers and has found that while they show

a wide range of quality, the best ones are considered suitable for

permanent record use. Dr. Robert C. Binkley is making an extensive survey, for the Joint

Committee on Materials for Research of the Social Science Council

and the American Council of Learned Societies of methods for reproducing records, which should yield very comprehensive data.

" Crabtree and Ives, Jour. Soc. Motion Picture Eng., vol. 15, p. 289, 1930.
26 Miscellaneous Publications, Bureau of Standards

XII. RECAPITULATION OF RECOMMENDED PRACTICES

The National Archives Building, Washington, D.C., is an exemplification of the more important practices for the preservation of records

recommended in the foregoing. In planning this depository of

Government records, these recommendations have been followed, and

use has been made in general of the most advanced scientific, engineering, and architectural knowledge, to safeguard the records. A large

air-treating system capable of handling 330,000 cubic feet of air per

minute will insure the purity and proper tempering of the atmosphere

throughout the building. A feature of this system will be the washing of the air with an alkaline solution to remove positively any acidic

contamination which might otherwise find its way into the storage

space. The pH of the wash water will be maintained at 8.5 to 9.0. It is planned to maintain a relative humidity of 55 percent in the

storage spaces, and of 45 percent in the work rooms. The latter

condition is the better adapted to human beings. The temperature

throughout will be kept at 70 F during the winter and 80 F during the summer. The higher temperature during hot weather is more

economical, and is more healthful for the personnel as it avoids sudden

exposure to too great change in temperature in entering or leaving the

building. Continuous maintenance of the humidity within 2.5 percent and of the temperature within 1° above or below the chosen

conditions is believed feasible. The temperature and relative humidity recommended were chosen because they represent a range in which

the substances stored exhibit good strength and flexibility and because

such conditions are excellent so far as the comfort of workers subjected to them is concerned (see Air Conditions and the Comfort of

Workers, Industrial Health Series, No. 5, Metropolitan Life Insurance

Co., New York). The growth of molds and fungi is minimized under

these conditions.

Daylight is excluded from the storage spaces of this building; the

necessary illumination is supplied by small incandescent lamps turned on only as needed. Another interesting precaution is the use of

glazed tile and the encasing of concrete columns in nonferrous metal

to minimize abrasive dust. Coated or nonferrous metals are used

where metal is required in the storage spaces to eliminate the necessity

of repainting, which would be hazardous to the stored records.

Stored material should never be removed from the purified air in

libraries as it will retain acidity that may be acquired from sulphur

dioxide in polluted air. New acquisitions of records should be fumigated to kill " bookworms" or other insect life that may be present. The use of "carboxide " in vacuum is desirable practice.

Frequent dusting with vacuum appliances will minimize the abrasive action of dust, as well as destructive bacteria and pests.

Japanese tissue paper has given good service when used as a protective covering for impermanent papers, and transparent cellulose acetate sheeting appears to be another suitable material for this

purpose. When reproduction of impermanent records is necessary,

the use of photostat prints on permanent paper is recommended.

It is realized that the complete use of all of the precautions mentioned is expensive. But this expense is not out of line with that of

purchase of record material and operating and housing expenses of
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Scribner J Preservation of Records 27

libraries, particularly when it is remembered that the preservation of

records is, or should be, the chief function of a library. In this connection, this report can well close with the following, which is quoted

from the article by Thomas M. Iiams:60 In October of the year 1902 the short-lived periodical known as the Bibliographer

published an essay entitled "Of Bibliophilism and the Preservation of Books",

by Henry French, later identified as the great collector, Robert Hoe. In this

article the author makes the unqualified statement that: Palatial fireproof buildings with imposing facades, monumental staircases and

lofty halls and reading rooms, elaborate and learned classifications and systems of catalogs, with ingenious machinery for the almost automatic delivery of books to

readers, however perfect and efficient, furnish no guarantee for the proper care of literary treasures. Washington, October 30, 1933.

«° See footnote 53, p. 22. O