Preservation of Paper-Based Library Materials

         One of the most complex issues facing libraries today is how best to preserve the materials that comprise their collections.  Since all library materials are not of equal value, decisions must be made concerning what should be preserved.  This process also involves setting priorities and determining appropriate preservation methods depending on the material needing attention and whether or not the original is to be saved.  Libraries tend to regard preservation as among their chief responsibilities and goals, but, simultaneously, they must be sensitive to the access and use needs of their patrons.  Thus, preservation often demands a balance between providing the protection an item needs and access considerations.1

         Before proceeding, it seems useful to briefly discuss and distinguish between the terms “preservation” and “conservation.”  According to the ALA Glossary of Library and Information Science, preservation is defined as “the activities associated with maintaining library and archival materials for use, either in their original physical form or in some other usable way.” 2  Another source suggests that “preservation involves a wide range of activities, including the general conservation of important and rare books and documents, environmental control, and the training of staff in proper storage and handling procedures.” 3Current usage of these terms in library literature suggests that preservation is the broader and more encompassing term and tends to include conservation.  The latter term refers to the techniques and procedures used in the treatment of books and other documents to stabilize and maintain their original integrity.

         It is possible to identify three primary causal factors that commonly characterize preservation problems in libraries.  The first, which may be viewed as an internal factor, relates to the characteristics of the materials themselves, whose physical and chemical properties are inherently unstable.  Many library materials have organic components such as paper, cloth, and adhesives.  These organics have a natural aging process which will result in a gradual weakening of the molecular bonds over time eventually manifesting itself as physical deterioration of the book or other library material.  Another primary factor is the physical environment of the library where the materials are being housed.  Environmental influences which promote the deterioration of paper and other materials include high temperature, extremes in relative humidity, unfiltered light, pollution, and biological agents.  The latter group includes fungi (mold and mildew), insects, and rodents.  The third primary causal factor relates to the nature of handling and use of library materials. 4   People themselves pose the greatest threat to the longevity of these materials because they are responsible for binding or packaging techniques, shelving procedures, processing and circulation practices, and the way library staff and patrons handle the materials.

         The primary contributors to the preservation problem as defined above coexist in a complex relationship within any library setting.  Therefore, it is important for those seeking solutions to preservation concerns acknowledge the interrelatedness and interaction of the various factors and develop strategies which are comprehensive and multifacted rather than limited and singular in application.

         Perhaps the most widespread preservation concern is the embrittlement of library collections caused by acid deterioration of paper.  Book printed since the mid-nineteenth century are deteriorating en masse with many surveys indicating that about 25 to 30 percent of the books in research collections are brittle.  For the Library of Congress alone, an estimated 3 million volumes have already become too brittle to permit circulation.5

         The sources of the acids found in paper are chemicals used in the manufacture of paper from wood pulp or those subsequently introduced from the environment.  The chemicals convert to a variety of acids which over time attack the cellulose fibers that make up paper, breaking it into smaller and smaller pieces, until the paper has lost all of its strength and durability.6   The concepts of paper permanence and durability developed as efforts were made to produce papers that were free of acid and that would resist the effects of aging. 7    In 1959, William J. Barrow, an early leader in the field of paper research,  predicted that most books produced during the first half of the twentieth century could expect a usable life of less than fifty years.8This prediction was based on his 1957 durability testing of a sample involving 500 books from libraries in the Richmond, Virginia area.

         This introductory discussion of preservation concepts will now move to an examination of several topics that are representative of the broad scope of library materials preservation.  First, techniques designed to preserve materials in their original format will be reviewed followed by a look at some common reformatting options.  Then, other practical approaches to addressing deterioration concerns will be covered.  Three established preservation and conservation organizations will be highlighted to focus on the availability of professional assistance with preservation issues.  The final section of the paper will offer a brief summary of preservation methodology as practiced in the W.L. Eury Appalachian Collection.

Techniques for Preserving Library Materials in Their Original Format

        Over the years, deacidification procedures have been developed that will neutralize the acids that cause paper to deteriorate.  These procedures also deposit an alkaline buffer that acts as a reserve to neutralize any acids that may continue to form. 9While deacidification will stabilize and sometimes even improve the appearance of paper, it cannot restore life to brittle paper.  Thus, deacidification is a preservation technique appropriate only for materials that have not yet become brittle.  Deacidification processes are classified according to the method by which the neutralizing and buffering agents are introduced: aqueous (water-based), non-aqueous (non-water solvent), and vapor.10The aqueous deacidification treatment is limited to loose sheets which makes it very labor intensive and thus expensive.  The individual sheets are dipped in a solution containing one or more alkaline compounds.  Aqueous treatments are not appropriate for items containing water-soluble inks, pigments, and dyes so each page must be tested to make sure it is compatible with the solvents being used.

         Non-aqueous deacidification solutions employ organic solvents rather than water as the solvent carrier of the alkaline buffering agent.  Advantages of this process as compared with the aqueous method are that it permits the treatment of many documents that contain water-soluble inks and other media, it may be used for sound bound volumes, and it is quick-drying.  Non-aqueous solutions may be applied to paper by spraying, dipping, soaking, or brushing. 11

         One of the better known non-aqueous technologies is that developed by Richard D. Smith of Wei T’o Associates.  It utilizes a liquified gas solution to thoroughly wet the pages of a book.  This system is operational at the National Library of Canada where approximately 40,000 volumes are being treated annually. 12
 A second well-known non-aqueous liquid technology is the Bookkeeper Process developed by the Koppers Chemical Company in 1981, and is now operated by Preservation Technologies, Incorporated. 13This process impregnates books with a solution containing magnesium oxide particles that neutralize the acid in paper and leave an alkaline buffer behind.14

         The vapor or gaseous deacidification technology that has received the most attention in the United States is the diethyl zinc (DEZ) process that was patented by the Library of Congress in 1975.  The Library worked for about twenty years to perfect this process which involved placing books in a vacuum chamber, using heat to reduce the moisture content of the materials, then introducing the DEZ vapors into the chamber which neutralizes existing acid and interacts with water to form zinc oxide.  The zinc oxide acts as an alkaline buffer that can neutralize any acids that may form after treatment.  Although extensive testing to the DEZ process was conducted from 1975 to 1994, safety and processing problems proved difficult to overcome.  The project was effectively halted when Akzo Chemicals, the company that had been contracted by the Library of Congress to perform additional testing of the process, closed the DEZ pilot plant in 1994.15

         The Wei T’o, Bookkeeper, and DEZ technologies are types of mass deacidification programs which were developed for the collective treatment of large batches of books.  Given the scope of the acid book problem, mass deacidification is a logical approach for rapidly increasing the number of books being treated and lowering the cost of treatment per book.

         While the deacidification process stabilizes paper, it does not restore lost physical properties.  Paper strengthening includes techniques or procedures that attempt to restore damaged or weak paper to a usable state, or to a condition of increased strength relative to its pre-treatment state. 16   Of the various paper strengthening procedures which have been or are under development, three will be briefly described here: cellulose acetate lamination, polyester film encapsulation, and graft copolymerization.

         Cellulose acetate lamination has been in use in the United States since the mid-1930s.  With this process, paper is sandwiched between two thin sheets of cellulose acetate film and heated under pressure in a hydraulic press. 17For this procedure to be effective as a preservation technique, paper must be deacidified before it is laminated.  Since the process lends itself to mechanization, it offers high output at a limited cost.  When used indiscriminately, however, the lamination treatment could prove harmful to certain types of documents.  In fact, one recent article described the lamination process as dangerous and difficult to reverse although heretofore it has been highly regarded as a preservation technique.18

         A second paper strengthening technology is the polyester film encapsulation treatment developed by the Library of Congress.  In this process, single sheets of paper are enclosed between two sheets of mylar or other polyester film, which are then sealed around the edges.19As with the lamination technique, paper should be deacidified before being treated with polyester encapsulation.  Because it is stable, easily reversed, and introduces no harmful products, the polyester film encapsulation process is preferred over cellulose acetate lamination.  Both encapsulation and lamination have limited application to treating books since sheets of paper have to be processed individually.

         Research has been underway for several years to develop a strengthening method for treating entire books or blocks of text.  One of these is the graft copolymerization process which is being developed by the British Library.  Simply put, this technique essentially reverses the breakdown of cellulose fibers in brittle paper by joining the shortened fibers with polymeric molecules which results in increased paper strength.20 This “whole book” technique has been successfully applied in the laboratory, and construction of a plant for full scale production is envisioned.

 Preservation of Library Materials Through Reformatting

         There are many situations when it is not possible to maintain a book or other library material in its original form.  The information found in materials that are heavily used, weak, or damaged is subject to being lost forever unless measures are taken to create a surrogate copy.  One widely used approach to this aspect of preservation is to produce duplicates in another, more stable format.  Two processes - microfilming and digitization - will be briefly presented here.

         For paper-based materials in particular, the “tried and true” method of preserving information is to reproduce it on microfilm.  Microfilming has been in existence as a preservation technique since the 1930's and over the past twenty years it has been the medium of choice for high-volume preservation efforts and funding.  The popularity of microfilming is attributable to several factors including its proven track record of quality reproduction, its existence as a stable medium (properly produced and stored silver halide microfilm has a life expectancy of 500 years), and its adherence to universally accepted standards.21 Microfilm captures a sizable amount of information in a compact format that can be easily duplicated and stored.  When originals are not to be retained after microfilming, a significant gain in storage space can be realized.

         For all of its many benefits, microfilm has one daunting drawback in that it is often perceived as a medium of storage rather than of access.22 The age of digital technology is spawning a demand for immediate access to information via electronic means.  Within a preservation context, the issue is becoming more than just insuring continued availability through longevity, such as exists with preservation microfilming, but to also preserve in a format that permits timely and convenient access to information, which is one of the attractive features of digital imaging or digitization.

         Digitization is an emerging technology which offers a powerful means for managing, storing, and retrieving information.  Within the past decade, this technology has been advanced by several converging developments including the proliferation of personal computing, increased accessibility of high-speed computer networks such as the Internet, and the enhanced availability of quality scanning systems.23 Scanned images can be accessed from remote sites and they can be organized in a variety of ways as well as linked to other electronic media.  Given the vast potential of digitization, interest in this technology as having preservation applications has intensified in recent years.  In addition to its many access advantages, digitization offers ease of manipulation and enhancement of images, preview capability, the ability to reproduce an image over and over without degradation, and flexibility in output.24An example of the latter would include situations where microfilm is created for preservation purposes from the digital images when a book is scanned.  These same digital images could also be used to produce a print copy or transmitted over computer networks to researchers at distant locations.

         On the other hand, there are significant disadvantages with digitization technology which must be acknowledged.  Perhaps the most troubling issue relating to digitization as a preservation method is that it is an evolving technology.25  Data storage formats and hardware systems configurations are constantly changing which raises the issue of long-term accessibility of the “preserved” information.  Another concern is the lack of commonly accepted protocols and standards for the use of digital technology in a preservation context.26 Maintaining access to the stored information will require periodic copying, refreshing, and migrating data to keep pace with future advances in hardware and software.  Functional indexing of digitally converted library materials presents an access and preservation concern.  Unless optical character recognition (OCR) programs have been used in the conversion process, the scanned images that exist on computer files are devoid of the indexing and bibliographic tools that permit convenient use.27

         Until these shortcomings have been addressed, many preservationists will be slow to embrace this new technology as a viable alternative to proven reformatting methods such as microfilming.

 Other Approaches to Preserving Paper-Based Library Materials

         Two other approaches for preserving paper-based library materials which warrant a brief review are preservation photocopying and use of acid-free or alkaline paper.
         To preserve the content of library materials that are unstable or subject to deterioration, photocopying with permanent and durable paper is an often-used option.  In order for a book to be reproduced in this manner, it must fall outside the current copyright restrictions.  Preservation photocopying must be used judiciously since the copying process can cause damage to fragile items; therefore, it is not an appropriate option for books with artifactual value.  In addition to photocopying onto alkaline paper, another requirement for producing a preservation photocopy is that the equipment used must meet United States government standards for image permanence in terms of the stability and strength of the ink bonding to the paper.28Photocopies occupy as much space as originals so there will not be any gain in storage space even if the originals are not retained.

         One proactive solution to the problem of acid deterioration of books is to use acid-free or alkaline paper.  Alkaline paper is more stable and, therefore, has a much longer life than acid paper.  Alkaline paper is brighter, more opaque, and smoother than acid paper and this provides improved print quality and color reproduction.  Two factors which essentially inhibit manufacturers from converting to alkaline paper production are the substantial retrofitting costs involved and the fact that book paper accounts for only a small portion of the total sales of paper makers.29  Nonetheless, public awareness of and demand for alkaline paper has increased the availability of this product in recent years.

 Organizational Resources Offering Preservation Information and Services

         There are many organizations at the state, regional, and national levels that are involved in various aspects of library materials preservation and conservation.  A well-established organization at each of these three levels will be briefly examined to present a sample of the resources available to assist with preservation concerns.  A state-level organization, the North Carolina Preservation Consortium, will be discussed first followed by information on SOLINET and the Library of Congress Preservation Directorate.

         The North Carolina Preservation Consortium is a not-for-profit membership organization with a mission of educating its members and others about the needs and methods of information preservation.  The Consortium was established in 1990 with a grant from the National Endowment for the Humanities.  Present financial support comes from membership fees and fees for services with partial employee support being provided by the School of Library and Information Sciences at North Carolina Central University.  This organization disseminates preservation information through its general interest newsletter and its responses to questions posed by records managers, librarians, archivists, and others.  A recently implemented program lends environmental monitoring equipment and literature to North Carolina records- holding institutions for a minimal fee.  Information on many common preservation concerns is accessible through the Consortium’s website which has a page devoted to frequently asked preservation questions and answers.30

         SOLINET, the Southeastern Library Network, Incorporated, is an Atlanta, Georgia based, not-for-profit regional network of over 800 member libraries and other information organizations.  One of SOLINET’s primary service areas is its Preservation Services division which is partially funded by grants from the National Endowment for the Humanities.  Through its preservation field services, SOLINET offers an information and referral service which provides up-to-date information and materials relating to preservation.  Workshops and presentations on specific preservation topics are conducted at conferences, for library school classes, and other special events.  SOLINET publishes both monographs and informational leaflets that are preservation-related.  SOLINET’s consulting services are available to its member institutions to assist with preservation program planning and implementation, disaster preparedness, staff training, environmental management, as well as other pertinent topics.31

         The mission of the Library of Congress Preservation Directorate is to assure long-term, uninterrupted access to the intellectual content of the Library’s collections.  The Directorate is comprised of several organizational units that collectively work toward accomplishment of the mission.  These units include the Conservation Office, the Preservation Research and Testing Office, the National Preservation Program Office, the Preservation Microfilming Office, the Binding Office, and the Preservation Office Library.  The Directorate is responsible for in-house preservation and conservation programs and it disseminates information in these areas nationally and internationally through publication of pamphlets and monographs and distribution of informational leaflets, audio-visual programs, and newsletters.  Also noteworthy is the Directorate’s participation in standards-setting organizations and its sponsorship of research on materials and conservation treatments.  Detailed information on a number of preservation techniques and issues is accessible through the Directorate’s website.32

 Preservation in the W.L. Eury Appalachian Collection at Appalachian State University

         The W.L. Eury Appalachian Collection is a repository for materials related to the Southern Highlands.  The strengths of this comprehensive, multi-disciplinary collection are folklore, ethnography, music, religion, local history, genealogy, fiction and African and Native Appalachia.33 The most intensive preservation efforts for this collection are being conducted in the closed stacks area.  Under the guidance of a special collections cataloger, a staff-level archivist and four part-time student employees are processing a variety of materials which will be housed as archives in the closed stacks.  The congressional papers of North Carolina Congressman and Senator James T. Broyhill are currently being processed and there is a backlog of about 100 much smaller archival collections to be processed.  A detailed procedures document provides specific guidelines for addressing the special needs for the various formats.  Photocopying and microfilming are two preservation methods being used extensively to insure continued access to rare and fragile items. Microfilming is the preferred reformatting technique because it is a reliable and proven method.34Embrittled materials showing the effects of acid deterioration are in some cases being treated with acid-free paper used as interleaving sheets and acid-free storage boxes to slow the deterioration process.

         According to Dr. Fred Hay, Appalachian Collection Librarian, digitization is not considered a viable preservation option for this collection.  He cites the predicted short shelf-life of CD-ROM’s, the challenges of upgrading obsolete software, and the necessity of migrating data as limitations of this technology which preclude its acceptance in many preservation settings.  Dr. Hay acknowledges that digitization greatly extends access and improves ease and comfort of use, but limited funds and staff make it difficult for him to consider it as an alternative or complement to the preservation microfilming and photocopying now being used in this collection.35


1.  Association of Research Libraries, Office of Management Studies, Preservation Guidelines in ARL Libraries (Washington, D.C.: Association of Research Libraries, Office of Management Studies, 1987), 12.

2.  Heartsill Young, ed., The ALA Glossary of Library and Information Science (Chicago:  American Library Association, 1983), 175.

3.  U.S. Congress, Office of Technology Assessment, Book Preservation Technologies (Washington, D.C.: U.S. Government Printing Office, 1988), 4.

4.  Association of Research Libraries, Office of Management Services, Expanded 1987 Edition - Preservation Planning Program (Washington, D.C.: Association of Research Libraries, Office of Management Services, 1987), 15-16.

5.  U.S. Congress, Office of Technology Assessment, Book Preservation Technologies,13.

6.  Ibid., 1-2.

7.  Mary L. Ritzenthaler, Preserving Archives and Manuscripts (Chicago: The Society of American Archivists, 1993), 26.

8.  Susan A. Adkins, “Saving Brittle Books: An Annotated Bibliography of Preservation Options,” Collection Management 13, no. 4 (1990): 54.

9.  U.S. Congress, Office of Technology Assessment, Book Preservation Technologies, 4.

10.  Ritzenthaler, Preserving Archives and Manuscripts, 144.

11.  Ibid., 145.

12.  Ibid.

13.  Ibid, 146.

14.  Will Dalrymple, “A Paper Chase: Technology Helps Library Save Its Paper Collections,” LC Information Bulletin 56 (April 1997): 148.

15.  Ibid., 149-51.

16.  Ritzenthaler, Preserving Archives and Manuscripts, 147.

17.  Chandru J. Shahani and William K. Wilson, “Preservation of Libraries and Archives,” American Scientist 75 (May/June 1987): 247.

18.  Abby Smith, “Preservation in the Digital Age: What is to be Done?” American Libraries 30 (March 1999): 37.

19.  Ritzenthaler, Preserving Archives and Manuscripts, 151.

20.  Shahani and Wilson, “Preservation of Libraries and Archives,” 249.

21.  Meg Bellinger, “The Transformation from Microfilm to Digital Storage and Access,” Journal of Library Administration 25, no. 4 (1998): 178-9.

22.  Ibid.

23.  Anne R. Kenney and Paul Conway, “From Analog to Digital: Extending the Preservation Tool Kit,” Collection Management 22, nos. 3/4 (1998): 65.

24.  Ibid., 72-74.

25.  Ibid., 74-75.

26.  Bellinger, “The Transformation from Microfilm to Digital Storage and Access,” 178.

27.  Kenney and Conway, “From Analog to Digital: Extending the Preservation Tool Kit,” 71.

28.  Library of Congress, “Preservation Photocopying,” Preservation

29.  U.S. Congress, Office of Technology Assessment, Book Preservation Technologies, 98-101.

30.  North Carolina Preservation Consortium, “North Carolina Preservation Consortium:  Preserving NC’s Documentary Heritage,”

31.  SOLINET, “Preservation Services,”

32.  Library of Congress, “Mission of the Preservation Directorate,” Preservation,

33.  Fred J. Hay, “The W.L. Eury Appalachian Collection of Appalachian State University,” Belk Library,

34.  Beth Cramer, Special Collections Cataloger, interview by author.

35.  Hay, “Re: Inquiry Regarding Closed Stacks Preservation,”


Adkins, Susan A. “Saving Brittle Books: An Annotated Bibliography of Preservation Options.”

Collection Management 13, no.4 (1990): 53-64.

Association of Research Libraries, Office of Management Studies. Basic Preservation Procedures. Washington,

D.C.:  Association of Research Libraries, Office of Management Studies, 1981.

________. Expanded 1987 Edition - Preservation Planning Program. Washington, D.C.:  Association of

Research Libraries, Office of Management Services, 1987.

________. Preservation Guidelines in ARL Libraries. Washington, D.C.: Association

of Research Libraries, Office of Management Studies, 1987.

Bellinger, Meg. “The Transformation from Microfilm to Digital Storage and Access.” Journal of 

Library Administration. 25, no.4 (1998): 177-85.

Cramer, Beth, ASU Library Special Collections Cataloger. Interview by author, October 25, 1999,  Boone, NC.

Dalrymple, Will. “A Paper Chase: Technology Helps Library Save Its Paper Collections.” LC  Information

Bulletin. 56  (April 21, 1997): 148-51.

Hay, Fred J. “Re: Inquiry Regarding Closed Stacks Preservation.” November 9, 1999. (November 9, 1999).

________. “The W.L. Eury Appalachian Collection of Appalachian State University.” Belk  Library. 1999. (September 22, 1999).

Kenney, Anne R. and Paul Conway. “From Analog to Digital: Extending the Preservation Tool  Kit.” Collection Management.

22, nos.3/4 (1998): 65-79.

Library of Congress. “Mission of the Preservation Directorate.” Preservation. 1999. (November 12, 1999).

________. “Preservation Photocopying.” Preservation. 1999.                                                 (November 12, 1999).

Lynn, M. Stuart. “Digital Preservation and Access: Liberals and Conservatives.” Collection  Management. 22, nos.3/4 (1998): 55-63.

North Carolina Preservation Consortium. “North Carolina Preservation Consortium: Preserving  NC’s Documentary Heritage.” 1999. (October 25, 1999).

Ritzenthaler, Mary L. Preserving Archives and Manuscripts. Chicago: The Society of American  Archivists, 1993.

Shahani, Chandru J. and William K. Wilson. “Preservation of Libraries and Archives.” American  Scientist. 75 (May/June 1987): 240-51.

Smith, Abby. “Preservation in the Digital Age: What is to be Done?” American Libraries. 30  (March 1999): 36-9.

SOLINET. “Preservation Services.” 1999 (November 11, 1999).

U.S. Congress, Office of Technology Assessment. Book Preservation Technologies. Washington,  D.C.: U.S. Government Printing Office, 1988.

Young, Heartsill, ed. The ALA Glossary of Library and Information Science. Chicago: American  Library Association, 1983.

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©David L. DeHart, Boone, NC (1999)