A Paper Conservator's Evaluation of the Bookkeeper Deacidification Process

Wendy Bennett

The Bookkeeper deacidification process is assessed by a paper conservator. The treatment is impressive for the minimal preselection of materials, improvement in general cleanliness of the books, lack of observable color changes in all book components, lack of discernible odor, and absence of physical distortion of the book block. The presence of small clamp impressions in several of the book covers, the slight chalky feel of some of the book pages, and an increased tendency of the printing inks on coated paper to rub off slightly are the less desirable qualities of this deacidification process as it was tested in 1993. It should be noted that PTI has been continuing to develop and improve their product since the time of the test.


This section of the report presents an evaluation of the Bookkeeper deacidification process from the point of view of a conservator. Typically, the treatment of acidic paper materials accounts for a large percentage of a paper conservator's workload. Some of this time is spent in an effort to deacidify and stabilize papers damaged by the destructive process of acid degradation. This gives the paper conservator a unique perspective from which to evaluate a mass deacidification process such as Bookkeeper.

There are two main contributors to the making of an acidic paper: one is airborne pollution and the other is "inherent vice," i.e., the original materials composing the paper (chiefly lignin and alum-rosin sizing) are inherently poor quality. In addition to acidity from atmospheric pollution and the manufacturing process, acidity in paper can be the result of proximity to poor quality secondary materials such as ground wood pulp cardboard, wooden backings and cross-linked glues or pastes. Heat and moisture tend to catalyze the degradation process, i.e., unregulated temperature and humidity, a situation common in many libraries, historical societies and archives, speed up deterioration. If the acidic process is allowed to continue unchecked, originally flexible papers will readily break apart with even the most gentle handling. If paper is acidic, because of internal or external factors, conservation procedures can never completely reverse physical deterioration but can slow it down.

Paper conservators generally counter the effects of acidity in paper by raising its pH to about 8.5-9.0 by means of a final aqueous bath or aqueous spray application. Solutions of earth metal salts of calcium or magnesium such as calcium hydroxide, calcium carbonate, or magnesium carbonate are commonly chosen for the job. The alkaline reserve helps to neutralize the acidity in the paper and counters future reacidification from the storage environment.

This process is similar to what Bookkeeper is attempting to do on a mass scale, although rather than using water, the carrier fluid for the MgO is a perfluorocarbon suspension in a surfactant. The presence of the surfactant combined with the agitation process ideally allows dispersion of the MgO to all parts of the books. Because other sections of this report feature the actual mechanics (Domach) and chemistry (Whitmore) of the Bookkeeper process, this section will focus on the look, feel and smell of the treated books and note how they compare with the control samples.


Twenty-five test books were cut in half. One half of each was labeled and dipped in the Bookkeeper solution at the PTI facility. The books ranged from pulp paper pages with newsprint covers and stapled bindings to engraved plates within a gold-tooled leather cover. A brief visual description of each book can be found in Appendix C. Additionally, marker pen was applied to several books, and post-it notes and paper clips to several others, to see how these three types of materials often found in libraries and archives would perform with Bookkeeper.

A condition evaluation checklist was drawn up. Treated and untreated book halves were compared for mechanical and cosmetic differences as well as for odor, abrasion testing, and the existence of surface deposits.



When the data was compiled from the empirical tests, it was noticed that items showing surface grime emerged slightly cleaner from the tank. In addition, in at least four instances, the treated book half was lacking the musty odor of the untreated half which suggests that though not water-based, the Bookkeeper solution somehow physically refreshes the books. The cleansing action of the surfactant would probably account for this situation. As a result of this occurrence, questions arose for the Team. What became of the dirt that was rinsed away from these materials? How often is the Bookkeeper solution filtered and recycled? Is the solution filtered completely enough to avoid deposition of dirt on other materials? The fact that the books emerged cleaner and free of odor is interesting and reassuring for both librarians and archivists.


None of the post-it notes or paper clips showed any change in appearance between treated and untreated book halves. None of the ordinary underliner marker inks changed colors. There was a change in the ink of a blue felt tip marker applied to the text previously (not by Bookkeeper evaluators) which turned green on the test half of book. It was discovered that this marker was pH sensitive. Consequent testing revealed that the color change was common when this ink was exposed to alkaline materials, in general, and not to the Bookkeeper product, in particular. It should not be considered a problem except, possibly, for other pH sensitive pigments or inks.


Although the deleterious effect of a low pH on paper is commonly acknowledged, aside from possible changes to inks and media at pH levels past 10, the effects of too high a pH seem less clearly agreed upon and understood. Apart from concerns about media, Some1 believe that cellulosic materials might be damaged by high alkalinity (pH 9.5 and above) while others2 feel that it is not paper degradation but the possibility of color change that presents the most risk at elevated pH levels. Conservators have noted color changes to pigments, dyes, and inks at pH levels higher than 10.0 as well as deterioration of the paper supports, especially those containing ligneous wood pulp. Therefore, a critical eye was turned to the test books with regard to color change. The empirical testing revealed that none of the Bookkeeper treated materials showed any observable color change whatsoever, except for the aforementioned pH sensitive marker.

In regard to concerns about possible damage to cellulosic materials from the high pH, it was noted on visual inspection that none of the tested book papers or covers exhibited physical degradation or damage. Several questions come to mind concerning the high pH created by any deacidification process. Is pH exceeding 9.5 too high for book papers? Is the sudden change from an initial pH, possibly as low as pH 3, to one as high as pH 10 too drastic a shift? What are the long-term effects, if any, on library and archives materials from the magnesium compounds used to achieve the pH seen in the Bookkeeper process? These are questions that should be asked of any deacidification agent and that can be addressed in further studies. Alkaline Reserve The Library of Congress requires a permanent and stable alkaline reserve meeting a minimum amount of 1.5% CaCO3 equivalent. They will also consider processes which introduce a lesser concentration of alkaline reserve provided that they offer equal protection against atmospheric pollution. However, Bookkeeper does meet the Library's minimum specifications. In sixteen out of twenty-five treated books, the physical presence of the alkaline reserve was noted by empirical testers, who characterized it as variably "gritty" or "chalky." This phenomenon was especially observed in books and book covers made of coated papers. Even though examiners did not, at any time, feel compelled to leave the testing room in order to wash hands, in retrospect, it might have been helpful to clean hands after handling a book so as to get a "fresh feel" of each subsequent book.

The presence of the alkaline reserve was subtle but nonetheless noticeable to the committee members on 64% of the books. This raises the question of whether the alkaline reserve could be adjusted slightly to retain more of the original "hand" of the paper while still meeting the Library's specifications. Aside from the aesthetic concern of how the alkaline reserve affects the feel of the paper, the Team raised issues of health and environmental safety which were referred to the EPA.

The Bookkeeper vendors stated that the MgO does not pose a health risk. PTI characterizes magnesium salts as "practically non-toxic by oral administration,"3 though they do report that acute exposure to large amounts of MgO in a particle size exceeding the one used in Bookkeeper can cause respiratory tract irritations. Karl P. Baetcke, Chief of Toxicology Branch I, Health Effects Division, EPA, states that in "...address[ing] the use of MgO...no concerns were expressed."4 Rub-off and Abrasion Testing When a soft cotton ball was rubbed gently in a circular motion on the treated book papers, a few of these materials, particularly colored plates on coated papers, showed more rub-off of some colors of ink than seen in the corresponding control group. Furthermore, the pressing of a finger to the surface of the dark-colored plates on treated, coated paper left an impression, but the inks above the surface did not smear or show softening when in contact with bare fingers. Deciding that this development required more systematic testing, the Team took a selection of books to the Graphic Arts Technical Foundation (GATF) in Pittsburgh, PA, for further evaluation.

Review of toxicological data submitted in support of Preservation Technologies, Inc., proposal for a mass deacidification process. Five books were selected for abrasion testing. A variety was sought, including several printed on the coated paper stock that presented the most problems in initial rub-off tests. In one case, the color on the cover of a book showed posttreatment color transfer, but because the cover was too thick for placement on the testing apparatus, this book could not be tested. The books that were selected are as follows:

#4 text block ink on noncoated paper

#9 colored plates on coated paper; black and white text

#19 color plates on coated paper; black and white text/plates on coated paper

#21 black and white illustrations/text on coated paper

#24 color plates on coated paper.

The Gavarti Comprehensive Abrasion Tester (ASTM D5181-91) was used to analyze the rub-off. In this test, a four-inch square sample of 20# bond paper was placed facing an identically sized sample from each of the test books. These materials were held rigidly by the machine's instrumentation while moving them rapidly up and down for twenty-five seconds. The 20# bond paper was then examined for offsetting of inks. In a few test cases, a density meter was employed to determine the relative lightness value of the abraded samples. Because the density meter was not sensitive enough, all colors registered at approximately the same value. (Black/cyan/magenta/yellow all registered approximately 1.5.) For this reason, testing of lightness values was discontinued.

In each case, the rub-off from the treated samples of coated papers was visibly darker than those of the untreated controls. Although the noncoated papers fared better, decreased rub resistance was also noted in the selected posttreatment noncoated papers. Since there is currently no way to scientifically quantify the extent of the rub-off by the Gavarti tester, it was, by visual examination alone, noted that the samples treated by the Bookkeeper process displayed approximately two to three times as much rub-off as did the controls. In addition, there was perceptible abrasion to the samples as a result of the testing that took the form of tiny striations on the surface of the paper. These interruptions to the printed surface of the paper were present in the control samples as well but were slightly more obvious in the treated samples, suggesting that the particles of magnesium oxide may have abraded the surface coating of the paper and taken some of the ink along with them. It is important to note again that no smearing of inks was observed, but rather it was the friction of the magnesium hydroxide particles against the surface coating of the paper that in all likelihood caused the rub-off. Granted, library books in general circulation will not be subjected to the strong friction of the Gavarti apparatus, but the question arose in the Team of what the long-term effects could be of more subtle actions such as page turning and photocopying? If the process seems to cause abrasion to the surface of coated book papers, is the process at all microscopically abrasive to the paper below the coating? Would there be any potential for damage to the sizings, adhesives, glues, thread, and other binding components found in library materials? It should be noted that the grittiness or chalkiness commented on previously is probably the same phenomenon causing this rub-off. Clearly, this is an area that may call for further research and testing.


Another posttreatment phenomenon was the appearance of small indentations visible on the corner edges of the covers of seven books. This apparently occurred because the clamps used to fasten the books to a dot-perforated grid left two thumbnail-shaped impressions on either side of the cover. Though changes such as these to the original appearance of an object are unacceptable from a conservation point of view and are grounds for complaint, the problem has been addressed in the latest version of the Bookkeeper process. Because the new development falls outside the time frame of the current report, future testers should pay attention to the possibility of impressions caused by equipment.


If chemical and physical testing reveals that the Bookkeeper process successfully and safely deacidifies books, the concerns raised here do not warrant rejection of the process. The book halves in the study that were treated by the Bookkeeper solution were impressively similar to the untreated halves in almost every way. True, some of the treated halves do feel slightly chalky, but this phenomenon seems to be the baseline for materials deacidified with magnesium compounds when used in a nonaqueous suspension. Further testing will determine if the clamp impressions and decreased rub resistance seen in test books treated in August 1993 are present in materials processed using the latest Bookkeeper technology. Since the vast majority of general circulating library materials, such as those represented by our test batch of twenty-five books, does not include rare or special collections material, the Bookkeeper process does represent a viable solution to the rapid physical deterioration plaguing most library materials today.

Some of the most pressing issues to arise from the consideration of the Bookkeeper deacidification process are those related to library and archival preservation and collection management. No deacidification process will be effective or suitable for all collection materials. Those librarians who choose to make use of mass deacidification, one of many viable choices for preserving collections, must understand the process and have realistic expectations about its capabilities and its effects. In her effort to address these issues, the rare book librarian has pointed out the need to communicate, evaluate, and to work in partnership with the process vendor to ensure the best possible outcome.

Issues to be addressed include the appropriate selection of material for treatment, the logistics of shipping and receiving, the care and handling of collections during treatment, and the examination and monitoring of treated items by libraries or archives.

Additional opportunities for cooperation and dialog among vendors, librarians, and scientists are apparent. How will libraries pay for deacidification? Should there be a coordinated effort nationally to deacidify primary resources as well as those important to local collections? What scientific issues related to deacidification remain unexamined? In what venues might materials be treated to ensure cost-effectiveness, i.e., regional centers, library binding companies, individual libraries, or archives?

The following report raises and addresses many of the issues important to librarians and archivists. It is hoped that the larger conservation and preservation communities will consider them and the others which will arise.

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