An Evaluation of the Bookkeeper Mass Deacidification Process

Technical Evaluation Team Report
For the Preservation Directorate, Library of Congress

Pittsburgh, PA
September 22, 1994

Technical Evaluation Team

Sally Buchanan, M.L.S., Chairperson
Associate Professor for Preservation
School of Library and Information Science
University of Pittsburgh

Wendy Bennett
Paper Conservator
Carnegie Museum of Art

Michael M. Domach, Ph.D.
Associate Professor
Carnegie Mellon University

Susan M. Melnick, M.S.I.S., M.L.S.
Editor and Compiler
Volute Preservation Management Associates

Charlotte Tancin, M.L.S.
Librarian and Research Associate
Hunt Institute for Botanical Documentation
Carnegie Mellon University

Paul M. Whitmore, Ph.D.
Research Center on the Materials of the Artist and Conservator
Mellon Institute
Carnegie Mellon University

Library of Congress

Kenneth E. Harris, Preservation Projects Officer

Chandru Shahani, Ph. D., Preservation Research Officer

Section I - Summary

An Evaluation of the Bookkeeper Mass Deacidification Process Technical Evaluation Team Report


The Technical Evaluation Team established by the Library of Congress has evaluated the Bookkeeper deacidification process and unanimously concludes that it demonstrates the potential to meet the requirements for mass deacidification as defined in the RFP issued in 1993 by the Library of Congress (Library). The Team also recommends that Preservation Technologies, Inc., (PTI) of Glenshaw, PA, be supported for further research and development by the Library.

Bookkeeper has already met many of the Library's specifications. The process deacidifies books, leaving an alkaline reserve, without decreasing paper strength. There is potential for scaling up for mass treatment, and the costs of doing so are not excessive. Neither human health nor environmental safety is compromised. The minor physical damage caused will be acceptable for most research collections. As was expected, there were problems and concerns identified as a result of the test procedures, conducted in August 1993, that suggested the advisability of additional research and testing.

Team members have written individual reports following this summary which are the body of the evaluation and report to the Library. It is important to note that research and development have continued over the past year since the initial test at the PTI facility. PTI has worked to refine and develop both its process and its technology, and observers would find in September 1994 a different environment than that described by the Team members in their reports. PTI's report is included as Appendix E.


The Pittsburgh-based Technical Evaluation Team was appointed in 1993 to work with the Library and PTI to assess Bookkeeper and its potential to meet the Library's specifications. The Team had the responsibility to establish a testing protocol based on the guidelines in the RFP. The charge to the Team was to evaluate Bookkeeper's effects on test materials at a specified period of time and to report on those results to the Library of Congress and the library and archive communities at large.

Sally Buchanan was asked to chair the Technical Evaluation Team. The remaining members of the Team, selected in recognition of the multi-faceted nature of the evaluation process, included Wendy Bennett, Michael Domach, Ph.D., Susan Melnick, Charlotte Tancin, and Paul Whitmore, Ph.D. Because of the range of expertise represented by the Team, the consideration of Bookkeeper was able to proceed on a number of levels.

The work of the Team was to culminate with a fully documented report on the efficacy of the Bookkeeper process. This report is the result. It will be published by the Library for public information and education. Kenneth E. Harris, Preservation Projects Officer for the Library of Congress, represented the Library in the endeavor. Chandru Shahani, Ph.D., Preservation Research Officer for the Library, worked with the team during the evaluation process. PTI has made all relevant proprietary information available to the Team as well as the time and expertise of its research staff. The cooperation of the staff of the Library of Congress, Preservation Technologies, Inc., and the Technical Evaluation Team members made this report possible.

The Library also contracted with the Institute of Paper Science and Technology, Inc. (IPST), in Atlanta, GA, to run independent tests on books treated by the Bookkeeper process. The detailed report from IPST is found in Appendix A.


Mass deacidification is a tool that many librarians and archivists had anticipated could be used to help combat the serious problem of the acidic collections in the nation's libraries and archives. While brittle materials were being identified and reformatted for preservation, there was also the troubling question of what to do about the millions of acidic but not yet brittle books and records inexorably deteriorating in the retrospective collections.

The Library of Congress responded over a decade ago by developing the DEZ process. Its potential seemed highly promising. Testing and experience, however, taught that it had drawbacks which required further research. Other deacidification technologies also showed potential, but none met all the needs or the expectations of the library and archival communities. Many had hoped that any process marketed would be totally effective, safe for users and environment, universally acceptable for collection materials, and cost-effective. Despite these expectations, it is unlikely that one process will ever be appropriate for all library or archival materials. Selection may depend upon process parameters, specific collection needs, and types of materials to be deacidified.

Further, different kinds of decisions related to acidic collections may have to be made by collection experts. For instance, is mass deacidification, which significantly slows the degradation of paper, the best solution even though it may result in some physical changes to the book or paper? Is controlled environmental storage, which causes no visible physical change in paper or books but is less aggressive in slowing deterioration, a better choice? The likely event is that librarians and archivists will make use of all possible options to ensure the preservation of the national collections.

Over the past five years there have been useful and reliable tests conducted on most available mass deacidification processes by conservators and scientists from several countries. Gradually, the growing body of knowledge has made it possible for librarians and others to begin to make the informed decisions necessary to protect as well as preserve collection materials. The Library mass deacidification program has been pursuing two initiatives over the past 1993-94 year. One was to continue to work with the Akzo Chemical Company in Texas on refinement of the DEZ deacidification process. This came to an end when Akzo made a decision in December 1993 to withdraw from the deacidification business.

The second initiative sought to encourage and evaluate the development of other technologies. In keeping with itscongressionally approved plan to assist the development of emerging processes that have the potential to preserve its collections, the Library published the RFP in 1993. PTI, the sole respondent to the Library's advertisement of the availability of its evaluation and testing program, submitted Bookkeeper, originally developed by the Koppers Company, Inc., and patented in 1985.


The Technical Evaluation Team began work in May 1993 to create a schedule, to define the testing protocol, and to decide upon appropriate test materials. The schedule established by the Team acknowledged both the requirements of the Library and the needs of PTI which, during the summer of 1993, was installing the new technology that was to be used for the test run. As first planned, the work of the committee was to be finished by the end of 1993, with the report available for distribution in early 1994. Due to the time required for contract procurements, the independent testing by IPST of the deacidified books, and other responsibilities of the Team members, publication of the report was delayed.

Team members, according to their respective expertise, assumed responsibility for separate aspects of the review process. The Team defined the testing protocol in terms of three screens, as explained below, through which Bookkeeper would have to pass.

  1. First, and most important, the mass deacidification process had to meet the Library of Congress specifications for efficacy, alkaline reserve, and completeness of treatment. Paul Whitmore had responsibility for definition of tests to be done, in addition to those required by the Library, as well as for the interpretation and discussion of the data resulting from those tests.
  2. Second, the process had to meet specifications applicable to process engineering criteria, its ability to be scaled up, and its environmental impact, toxicity, and health effects. In his report, Michael Domach reviewed the Bookkeeper process technology as it existed at the time of testing. The EPA report is included in Appendix B.
  3. Third, in order to be considered safe for library materials, the process could not result in any harmful or unacceptable side effects. The evaluations of this third screen were designed to detect odor, discoloration, distortion of paper and textblocks, as well as any other unwanted reactions caused by the process. Charlotte Tancin and Wendy Bennett addressed these issues in their reports. The Team wanted to identify those properties of library materials which might be adversely affected by deacidification. In the development of this set of parameters for consideration, the Team polled the preservation and conservation communities via the Conservation DistList, an online forum in which members can communicate through the Internet. Respondents suggested areas of concern related to mass deacidification. Selecting Materials for Testing

The Library has focussed its testing of mass deacidification processes on bound materials and has created the LC blue test book as a standard unit for evaluation. Unlike ordinary books, these volumes consist of bound blank sheets of a variety of paper types.

Because other deacidification methods have caused a variety of undesirable side effects1, and in response to concerns raised through the Internet inquiry, the Team expanded the original test batch beyond the mandated LC blue test books. Members decided to consider the effects of Bookkeeper treatment on a collection of books which represented a "typical" library collection. The Team selected twenty-five used books, collected from various libraries, to be added to the test batch. These books presented a range of publication dates, countries of origin, paper types, ink colors, binding methods, plate types, and other physical components. A list of these books can be found in Appendix C. These materials were not sent to IPST for testing after treatment.


On August 30, 1993, the entire set of test materials, both the LC blue test books and the twenty-five additional books, were processed by PTI in the presence of the Technical Evaluation Team. Each of the twenty-five used library books had been cut in half, perpendicular to the spine. One half of each volume was to be processed, and the untreated half was retained as a control.

The LC blue test books and both halves of the library books were transported to PTI where they were unpacked in the Bookkeeper plant. The half of each library book to be treated was labelled with the Bookkeeper label. The Team had, for testing purposes, placed a variety of items in the books. The Team also marked some of the books with a variety of markers, pens, and pencils, in order to observe any effect of the Bookkeeper process on these markings.

After the materials had been deacidified, the treated and untreated halves of the bisected volumes were placed together for comparison. They were also photographed for documentation.


The LC blue test books were sent to the Library of Congress for limited testing and aging and were then forwarded for independent testing to the Institute of Paper Science and Technology, Inc., Atlanta, GA. A list of tests is provided in Appendix D.

The twenty-five bisected library books were scrutinized by committee members. The treated halves were compared with their untreated halves in an effort to detect side effects of the Bookkeeper process. After this initial examination, the twenty-five books were subjected to further testing by Paul Whitmore. In December, several books were also taken to the Graphic Arts Technical Foundation, Pittsburgh, PA, for abrasion testing of printed plates on coated paper on the Gavarti Comprehensive Abrasion Tester, according to ASTM D518191.

While waiting for test results, the Team served as a liaison between the Library and PTI. The members worked with PTI, explicating areas appropriate for research and development which had become apparent during the evaluation process. Issues of importance to the preservation and conservation communities were also communicated to PTI. Then, as the testing and evaluation data became available, each member of the Team addressed the relevant data in a section of the report related to that individual's area of expertise. Library of Congress Specifications

The charge from the Library to the Technical Evaluation Team was to evaluate the Bookkeeper deacidification process to determine if it had the potential for meeting the technical requirements for deacidification set by the Library of Congress. Among these requirements are the following:2

1. Efficacy

Through neutralization of acidic paper and incorporation of a suitable permanent alkaline reserve, the rate at which paper loses strength upon accelerated aging at 90 C/50% RH for up to 30 days, shall be decreased by at least a factor of 3.0, when the logarithm of the folding endurance is plotted against time in days. [RFP80-21 Requirement - C.2.1.4.] The permanence of the treated paper shall be increased by a factor of 300%.


a) Treated papers showed less degradation of mechanical properties than did untreated during accelerated aging. Treated papers from the test books generally retained their desirable performance properties for 2-4 times longer in oven-aging, comparable to the factor of 3 required in the Library specifications. Overall performance in the oven tests show benefits of the treatment.

b) The treatment did not measurably affect the physical appearance of the papers in the Library test books.

2. Completeness of Deacidification

After treatment, the average pH value will be between 6.8 and 10.4. Deacidification shall be demonstrated within each page, each book and throughout all books in a treated batch. [RFP9021 Requirement - C.2.1.7]


a) Treatment of all the paper types in the Library test books raised the pH of the sheets from a moderately acidic pH of 5.7-6.5 to alkaline levels ranging from 9-10. Subsequent oven-aging of the treated sheets caused the pH to fall slightly to 8.0-9.5.

b) Treatment which neutralized LC blue test books did not completely deacidify several of the old library books that originally may have been very acidic. Limited testing of the twenty-five library books selected by the Team revealed that Bookkeeper deacidification of highly acidic, older collections may require additional research into the process technology and some stricter bench marks for treatment.

3. Alkaline Reserve

Uniformity for a given paper type shall vary from specified optimal concentrations by no more than 20% between books and by no more than 20% between and within individual pages. [RFP90-21 Requirement - C.2.1.8] Alkaline reserve amount is not decreased by more than 0.5% calcium carbonate equivalent after aging for 30 days at 90 C/50% RH. The minimum amount of alkaline reserve shall be 30 milliequivalents per 100g (1.5% calcium carbonate equivalent.) [RFP90-21 Requirement - C.2.1.8] The process will result in an alkaline reserve of not less than 1.5% with stable and uniform distribution.


a) Alkaline reserves were somewhat lower than the Library's specifications (1.5%), but the initial value of the reserve did not fall during 30 days of oven aging. On some papers, alkaline reserves must be improved.

b) It would appear that the most immediate shortcoming of the Bookkeeper process involves the nonuniformity (as demonstrated August 30, 1993) of the treatment chemical to book materials rather than in the technology itself. Test results indicate that the Library test book papers contain an overall uniform deposit of magnesium oxide across the entire sheet with the exception of the gutter areas where only 30-50% of the average loading took place.

4. No Damage to Processed Materials and Media

No process-related damage to books. [RFP90-21 Requirement - C.2.1.10, C.2.1.11, C.2.7.12] The processed books will be evaluated for damage to the dyes, inks, or adhesives, for any process-induced odors, for loss of strength, or for significant change of color or degree of photosensitivity to the book paper as a result of treatment.


a) The treated books had no odor. Those demonstrating a pretest musty odor lost that odor during the treatment process.

b) There was no observable adhesive loss or damage on book spines or to shelf labels, security strips, book pockets, or plates.

c) There was no damage to book cloth or other covering material. A typical plastic book jacket acquired a light dusting of magnesium oxide. There was no softening of plastic or change of color. There was no damage to pamphlet binders. There appeared to be no damage to the leather on the two leather bound books.

d) There was no change of dye color in book cloth or in printing ink, internally or externally. There was no damage to gold tooling or gilded edges. Marker ink used for underlining text did not change color or bleed, with the exception of a pH sensitive marking pen. The Team noted there was some rub-off of colored inks from printed plates on coated stock. The inks did not transfer to hands or to adjoining pages but was discovered as result of abrasion tests.

e) There was no cockling of paper or distortion of boards, pamphlet binders, or textblocks.

f) There was some observable change in the untreated papers from the LC blue test books aged in a humid oven, causing some to darken and become less translucent. The Bookkeeper-treated book paper, aged in a humid oven, did not differ significantly. Color and translucency were neither better nor worse.

g) Slight chalking or white residues could be seen and felt on coated stock and detected by Team members on some other papers. This was not found instrumentally on the unprinted white papers of the Library test books.

h) The physical and mechanical actions involved in the Bookkeeper deacidification process did no harm to books, documents, or fragile bindings except for clamp marks that were detected on some covers.

i) Some books from the Team's set of twenty-five were "cleaned" during the deacidification process. Surface dirt and debris such as dead insects floated to the surface of the treatment tank. There was no effect from rubber bands and paper clips placed in the books before treatment.

j) Pretreatment drying or other conditioning of materials is not necessary.

5. Potential to Treat Books on a Mass Scale

The deacidification process and production facilities demonstrate potential for scale-up to a mass deacidification process. [RFP90-21 Requirement - C.3] In addition, there were to be no health hazards or any serious environmental impact from the process.


a) The treatment technology observed in August 1993 was not designed as a mass process. A detailed description of the process and equipment can be found in the Domach report. There is reason to believe that scaling up should not be a mechanical problem. New equipment has been designed and is being tested.

b) A distinct advantage of the Bookkeeper process as compared to others is the modest estimated start-up costs for a new treatment facility.

c) Because the treatment process is not hazardous, a facility could be located in a local institution, a business, or a regional center, or it could be portable and delivered on site to treat collections.

d) The issues of shipping, receiving, handling, and packing collections must still be addressed.

e) The selection of appropriate materials for mass deacidification of research collections must be considered by librarians and archivists. Education is in order so a common understanding of needs, costs, and ability to support mass deacidification is reached. That mass deacidification is not an appropriate process for brittle, rare, or special collections must also be understood by librarians. Archivists will have different selection criteria as most of their collections are unique.

f) The EPA evaluations of the process find no serious health hazards or negative environmental impact. (Appendix B)

The Team agreed, based on their findings, that Bookkeeper has potential to meet the Library's specifications. At the same time, however, Team members identified areas which may be appropriate for further research and development by PTI, such as those mentioned by Bennett, Domach, and Whitmore. Those specified by Tancin will be of particular interest to librarians who are considering mass deacidification for their collections.

Domach discussed the factors which may contribute to nonuniform distribution of MgO particles throughout the text during treatment. Whitmore agreed that problems of controlled application had not been solved in August 1993. Because older library books which may have been very acidic before treatment were not satisfactorily neutralized, he also suggests that older and acidic papers, rather than the less acidic papers of the LC blue test books, be used to set bench marks for developing conservative process parameters.

As a conservator, Bennett remarked on the palpable residue that she found on some treated papers. Her observations that, following treatment, colored inks on coated stock showed a slightly increased tendency to rub off were supported by further testing on the Gavatri Comprehensive Abrasion Tester.

Librarians, if they are to exploit fully the potential benefits of mass deacidification, according to Tancin, must be prepared to structure guidelines for pretreatment selection and for care and handling of materials during treatment. She also emphasized need for the establishment of protocols for pretreatment testing and posttreatment monitoring of collections. These contributions, among the others found in the individual reports, should provide PTI, the Library, and the library and archival communities with direction for improvement and use of mass deacidification in general and Bookkeeper in particular. Conclusions

The PTI Bookkeeper deacidification technology meets the criteria set by the Library of Congress for a process which shows potential for meeting their specifications. Problems identified as a result of IPST testing or the Team's observations can be addressed as part of the ongoing research and collaboration. The process is a clean one causing harm neither to the environment nor to materials tested. Questions which arose during the testing procedures remain to be answered. The library and archival communities may find that a choice has to be made between a less aggressive mass deacidification process that results in little or no physical damage or other undesirable side effects and one that is chemically more aggressive, causing some observable physical damage. Preservation and collection experts may take advantage of both, based upon condition assessment, the importance of physical appearance, and tolerance for specific technological strengths and weaknesses.

The chemistry of mass deacidification, its scientific value, and the solution of problems resulting from treatment are critical topics in the quest to find an answer for the dilemma posed by the millions of acidic books and records in this nation's libraries and archives. The significant part that acidity plays in the rapid deterioration of paper has long been recognized. Deacidification as a potential solution has been scientifically investigated over the last fifty to sixty years in several countries. Indicative of the effort made to understand and resolve the challenges raised by acidic paper and to exploit the potential of deacidification as an answer is the existence of the large body of literature on the subject.

Section II -- Reports

Reporting on the process technology and the ability of PTI to scale up in response to the Library specification for a mass treatment facility required the expertise of a chemical engineer. He also commented on the process chemistry; and his questions related to health effects, toxicity, and environmental safety were forwarded to the Environmental Protection Agency. The charge, made by the Library to the Team, to assess Bookkeeper at the time of the August 1993 test run, had to be balanced with the Team's realization that new developments would make some of their comments obsolete.The Team found itself playing two roles. While preparing and writing a report for the Library, the Team was, at the same time, serving as a communications link among PTI, the Library, and the outside library and archival communities. As PTI continued research and development, incorporating feedback and ideas from the Team and the Library, it was essential that progress be monitored and described to the other Team members by the chemical engineer. His interactions with the PTI staff enhanced the Team's understanding of increasingly complex technology and process changes.

Technical Evaluation of PTI Mass Deacidification Technology
Michael M. Domach, Ph.D.

Evaluation of the Bookkeeper Process Chemistry
Paul M. Whitmore, Ph.D.

A Paper Conservator's Evaluation of the Bookkeeper Deacidification Process
Wendy Bennett

Mass Deacidification in the Library: A Rare Book Librarian Considers Bookkeeper
Charlotte Tancin, M.L.S.


*** Most of the following Appendices are not abvailable in the electronic version of this document:

Appendix A: Report of the Institute of Paper Science and Technology, Inc.

Appendix B: Report of the Environmental Protection Agency

Appendix C: Description of the Twenty-Five Additional Test Books

1. gold-tooled leather; gilt-edged; foxing on engraved plates; interleaved foxed, acidic tissue

2. Australia; fold-out, color-printed maps on hard-finish tissue; coated paper; yellow highlighting top/bottom on page 15

3. plastic book jacket; paper jacket; pyroxyline-coated publishers' binding

4. foil stamping on blue cover; typical size and publication date; marked with felt-tip marker and highlighter

5. red cloth binding; coated paper; gold tooling on spine; black and white plates; signatures

6. Eastern Europe; stapled; pulp paper; journal; rough paper cover

7. stapled; mimeographed

8. clear plastic cover; plastic spiral bound; plastic adhesive label on spine; photocopy

9. large size; black and white illustrations on text paper; color plates on coated paper; spine label; coated cloth binding

10. Gaylord pam binding; brown tinted ink; selin label; date-due pocket; book plate

11. India; journal; green paper cover; lavender-tinted paper; plates on white coated paper; sewn binding

12. sewn; plasticized cover; color illustrations; coated paper

13. China; journal; poor pulp paper; colored illustrations on coated cover paper

14. sewn; brittle; calendered; remainder of paper cover on spine; no other cover

15. South America; adhesive binding; blue-coated paper cover; good pulp paper

16. Jordan; stiff green paper plasticized cover; adhesive binding; calendered paper for text; black and white illustrations on coated paper

17. paper dust cover; cloth book tape spine; paper-covered boards; plain paper

18. bright blue cover; gold tooling on spine; colored maps on end papers

19. red paper cover, gold tooling; deteriorating tape on spine; bar code; color illustrations on coated paper; tinted pages and nontinted newsprint; thick large book; adhesive binding

20. Western Europe; mutilated; black cloth cover; gold stamping on spine; selin label; bar code; pulp paper; date-due pocket; stamped with red ink

21. typical trade paperback; thick; adhesive bound; plates on coated paper

22. badly repaired and falling apart; black cloth binding; clear adhesive tape on spine; bar code; block of plates on coated paper; maps on end papers, stamped with red ink; gold tooling on front cover is worn off

23. thick paper back; paper cover; signatures; adhesive spine

24. portfolio style; collection of color prints on coated paper mounted on one edge on calendered paper; boards exposed along spine; book cover is torn

25. plastic spiral bound; hand covered with brown paper wrapper; hand written title in black ink; bar code; call number label, date due pocket; original cover has mounted color illustrations; color plates on coated paper mounted on black paper; black and white illustrations and text on coated paper; exposed boards are faded black

Appendix D: Summary of the Tests Performed

Summary of the Tests Performed

A. Tests of process results: amount and distribution of applied particles

1. SEM pictures of deposited particles and uniformity of deposit on paper surfaces and interiors

2. X-ray fluorescence spectra for semi-quantitative measure of magnesium particle location

3. ICP/MS analysis to determine total particle deposit and uniformity of deposit (Also done on 4 library books which failed pH spot tests) 4. Cold extraction pH

5. Alkaline reserve

6. "Completeness of deacidification": indicator spot tests with 0.04% chlorophenol red

B. Tests of efficacy in oven aging

1. MIT fold endurance

2. Tensile properties (tensile strength, stiffness, stretch, tensile energy absorption)

3. Internal tear resistance

4. Zero-span tensile strength

5. Opacity

6. Brightness

7. Color (L*, a*, b*)

5. Retention of alkaline reserve

6. Viscosity DP

7. Hot alkali solubility

C. Tests of side effects

1. Measured properties above for unaged papers, treated vs. untreated

2. "Condition evaluation"

Appendix E: Report of Preservation Technologies, Inc.


1 Anne Liénardy, "Evaluation of Seven Mass Deacidification Treatments," Restaurator 15:1-25, 1994. 2 Library of Congress, Test and Evaluation of the Bookkeeper Deacidification Process in Support of the Library of Congress' Research and Development Efforts for a Mass Deacidification Process. Contracts and Logistic Service, 1993.

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