A liquid-based mass deacidification technology called Bookkeeper may help the Library win its war against acid damage in its paper collections.
Looking down into a Bookkeeper deacidification treatment cylinder. Books are mounted on racks and gently agitated in a milky suspension of magnesium oxide. They are only submerged for about 25 minutes. - Kenneth Harris
In January 1995, Congress authorized a two-year, $2 million initiative to treat some 72,000 books through the Bookkeeper process and also to help assess the effectiveness of other methods of neutralizing acids in paper. So far about 56,000 books have been treated and by early September, another 16,000 will have been through the process at a cost of about $11.70 per book.
The Bookkeeper process -- which impregnates books with magnesium oxide particles that both neutralize the acid in paper and leave an alkaline buffer behind -- follows the Library's 20-year effort to develop and refine another deacidification technology known as the diethyl zinc gaseous process.
Acidic paper threatens to destroy most of the Library's 17 million books and other large collections of paper-based materials.
"A majority of books here -- and in any library -- were printed on acidic paper and are in danger of embrittlement," said Chandru J. Shahani, chief of the Library's Preservation Research and Testing Division. "Unless they are deacidified, most of these books will become too brittle to handle within the next 50 years."
Paradoxically, most threatened paper was made long after some of the oldest of the Library's collections. The Library's oldest paper materials -- usually made from cotton rag -- register slightly acidic but degrade more slowly than woodground, pulp-based paper. Mills switched from rag to wood pulp in the early 19th century to increase the production to meet demand. Paper makers still use cotton today for high-quality stationery and U.S. currency.
"Impurities such as lignin, hemicellulose and hydrolyzed cellulose [all basic to the cellular structure of wood pulp] oxidize and produce substantial amounts of acidic degradation products," according to a Progress Report by Preservation Technologies Inc. of Cranberry Township, Pa., included as an appendix in the 1994 publication An Evaluation of the Bookkeeper Mass Deacidification Process: Technical Evaluation Team Report for the Preservation Directorate, Library of Congress. (For this report and other information regarding deacidification, see LC MARVEL on the Internet at //www.loc.gov/preserv/pubsdeac.html.)
Atmospheric gases can also react with the paper to form acids, the Preservation Technologies Inc. (PTI) report noted. PTI owns and operates the Bookkeeper process.
"These acids break down the cellulose, hemicellulose and lignin in the paper and form additional acids as by-products. These acids, in turn, catalyze further degradation, and therefore this process is termed autocatalytic," the report said.
Another treatment chamber used in Bookkeeper technology. Books are mounted on the large cradle and submerged. Bookkeeper equipment can be used to treat fragile and oversize books. - courtesy PTI Inc.
"This shortening of the average chain length of these paper components leads to a catastrophic loss of paper strength. It has been estimated that when 0.5 to 1 percent of the bonds are broken the paper will be virtually useless," it said.
In 1990 the Library published a set of technical specifications for mass deacidification. To be approved by the Library, a deacidification process must increase the useful life of paper by at least three times, as measured by physical and chemical tests performed after artificial aging at elevated temperature and humidity conditions.
The process and the treatment must be safe for library readers and the operators of deacidification equipment.
The procedure must not physically change or damage the paper or ink, and it must impregnate the paper with an alkaline reserve and deacidify completely all the pages in a book.
"Paper conservators generally counter the effects of acidity in paper by raising its pH to about 8.5-9.0 [below 7 is acidic] by means of a final aqueous bath or aqueous spray application," said paper conservator Wendy Bennett of the Carnegie Museum of Art in her article "A Paper Conservator's Evaluation of the Bookkeeper Process," appended to the Bookkeeper evaluation.
"The alkaline reserve helps to neutralize the acidity in the paper and counters future reacidification from the storage environment," she said.
In deacidification treatments, the alkaline agent is either dissolved or suspended in an inert liquid to which the books are exposed, or the agent is dispersed through a gas vapor that penetrates book material.
Any mass deacidification procedure treats many books at one time, instead of labor-intensive page-by-page spraying by conservators.
With the present Bookkeeper III equipment, PTI can deacidify a batch of eight books in each of four treatment chambers in two hours. Active exposure to the treatment chemistry lasts only about 25 minutes. The Bookkeeper process works best with standard, bound volumes in good physical shape. Preservation Projects Director Kenneth Harris and Mr. Shahani estimate that the "vast majority of LC collections" would fit these criteria. Extemely brittle, damaged books or books that are rare or very large must be treated by hand or reformatted.
Although the Bookkeeper process is harmless to most books, fragile volumes warrant extra caution, Mr. Harris and Mr. Shahani said. The Bookkeeper process submerges and gently agitates books in a liquid bath. The bath contains white, extremely fine magnesium oxide particles in suspension, an inert solvent carrier that allows the magnesium oxide to penetrate the book and a surfactant that disperses the magnesium oxide throughout the bath.
"This procedure relies both on the fluid transport through the book structure and on the sticking efficiency of the particles on a sheet to determine the amount, distribution and rate of particle deposition," Paul Whitmore said in his paper "Evaluation of the Bookkeeper Process Chemistry" in the Bookkeeper evaluation.
In an earlier test of the Bookkeeper process, an evaluation team appointed by the Library selected a wide variety of disposable books to test-deacidify. They cut each book in half so they would have an equivalent control sample. The uncut books stacked in the upper right-hand corner of the table are LC "blue books," which contain a variety of different types of blank test papers. - courtesy PTI Inc.
A panel of scientists and preservation experts who evaluated the Bookkeeper process at the Library's request are confident that the process does not damage or alter the appearance of the paper or the bindings of treated books. They are less sure about the deacidification reaction itself. Within the paper, magnesium oxide -- MgO -- and water react to form magnesium hydroxide -- Mg(OH)2 -- the compound that actually neutralizes the acids in paper.
"It is obvious ... that deacidification is possible when enough water is available to begin conversion of MgO. Complete neutralization can occur when the amount of Mg(OH)2 needed to neutralize the original acid in the book is present," according to the PTI report. "Additional conversion leads to the buildup of alkaline reserve material in the book and does not affect the time required to neutralize the acids initially present in the book," it said.
Chemists found that books exposed to accelerated aging and treated by Bookkeeper met the Library's preservation criteria for longevity. In a folding test, treated book paper lasted at least three times longer than similarly aged, untreated paper.
At least one hurdle remained, however, before the Library could begin its current 72,000-book "demonstration contract" with Preservation Technologies. Testers had found that Bookkeeper did not always adequately neutralize acid in the gutter area of the book, the edge of the page where the paper is bound to the spine.
To solve the problem, Mr. Harris and Mr. Shahani worked with PTI personnel to create a battery of experiments that manipulated some of the physical and chemical conditions of the process. Subsequent laboratory tests showed greatly improved results in deacidifying the entire mass of paper in the text block, including the gutters, of books.
But Bookkeeper is not necessarily the only solution. Gaseous carriers such as those used in the diethyl zinc process, can penetrate solids and deposit a uniform coating more easily than liquid applications, such as Bookkeeper. Mr. Harris and Mr. Shahani note in their 1994 evaluation Mass Deacidification: An Initiative to Refine the Diethyl Zinc Process that the gaseous process "can deposit high concentrations of alkaline reserve, extremely uniformly, regardless of the thickness or size of a book. All types of papers, including coated and dense supercalendered [highly finished] papers, are thoroughly treated."
The Library had tested the complex DEZ process from 1975 until 1994. (LC patented the DEZ process in 1975.). Besides safety problems that resulted in a fire in an empty chamber in 1985, the process resulted in other unpleasant side effects such as treatment-induced odors in books, visible iridescent chemical patterns on some test book covers and damage to labels.
The Library used the Akzo Chemicals (previously known as Texas Alkyls) pilot plant in Deer Park, Texas, from 1986 until 1994 to run an additional series of DEZ tests. Safety and processing problems were resolved; Mr. Harris and Mr. Shahani's 1994 DEZ report concluded, "Near-perfect treatment is achievable."
The current Bookkeeper machine evolved from early models as testing took place and improvements were made. Today's machine, with the capacity of 120,000-plus books annually, includes provisions for vertical agitation, vacuum drying and recovery of the liquid carrier. PTI has recently designed machines with both smaller and larger capacities.
However, this success was not long-lived. Akzo closed the DEZ plant and terminated its contracts with the Library and other institutions in April 1994, citing "only limited prospects for adoption of this process in the near future." As a result, although perfected, the gaseous DEZ technology cannot be applied without a significant capital investment -- an investment that no company or institution has yet been willing or able to make. (A large facility is not required with the Bookkeeper process.)
Various deacidification technologies continue to develop throughout the world. Institutions and companies are actively developing or initiating programs to create mass deacidification services in other countries such as Germany, France, the Netherlands, England, Switzerland, Canada, Japan, South Korea and China. Preservation Technologies' Bookkeeper process is now the only mass deacidification technology fully operational in the United States.
Regarding the contract with Preservation Technologies, Mr. Harris said that the Bookkeeper process is doing a good job so far of meeting the Library's technical requirements for deacidification. "It's gratifying," he said, "to see row after row of endangered books that have now been deacidified and safely returned in exact shelf list order without a single book being lost.
"The reward for all the hard work of Library staff is knowledge that, each month, we're able to save thousands of books from oblivion," he added. "Assuming proper storage and handling, deacidified books will be preserved and made available to future generations of researchers who will continue to rely on the Library of Congress as the responsible custodian of our cultural heritage."
After several years of testing different chemicals and concepts, and resulting alkaline reserve, pH level and fold endurance, Koppers was granted the patent for a deacidification method in 1985.
When Koppers chose not to develop the process further, it was sold to Richard Spatz (who had been president of Koppers Forest Products Group). He founded Preservation Technologies in 1990 with two associates, and his company was given an exclusive license.
-- from "A Gentle Approach to Deacidification with Preservation Technologies Inc.
