Volume 18, Number 8
Dec 1994

Two Deacidification Processes Evaluated; Reports Available from LC

[The Library of Congress recently evaluated the Bookkeeper and diethyl zinc processes. This brief summary of the two projects, which is dated December 23, was written by Kenneth E. Harris and Chandru J. Shahani, Preservation Projects Officers in the Preservation Directorate and the Preservation Research and Testing Office, respectively.]

Over the past two years, the Library of Congress continued its commitment to enhance and encourage the development of mass deacidification technologies through a two-part ActionPlan that was approved by Congress. Under Phase A of the plan, the Library pursued refinement of the diethyl zinc (DEZ) process. Phase B permitted the Library to offer a program of evaluation and testing to other promising deacidification technologies; under this provision, Preservation Technologies, Inc. (PTI) of Pittsburgh asked the Library to evaluate its Bookkeeper deacidification process. Copies of the reports on the two projects* are available from Kenneth E. Harris, Preservation Directorate, Library of Congress, LM-G21, Washington, DC 20540-4500 (202/707-1054; fax 707-3434; Internet KHAR@LOC.GOV.

With the DEZ process, the Library conducted a series of planned test runs in the Akzo Chemicals deacidification plant in Texas and succeeded in eliminating process-related problems that were experienced earlier with the DEZ technology. However, we note with disappointment that Akzo Chemicals withdrew from the deacidification business this past spring and terminated its DEZ license with the U.S. Commerce Department effective in September 1994. The Library has not requested Congressional support at this time for a DEZ initiative because of projected high DEZ capitalization costs and because of encouraging developments with the Bookkeeper process, which affords lower capitalization costs along with other attractive features.

Under the second phase of the Library's Action Plan, as indicated above, a Library-appointed evaluation team studied the Bookkeeper deacidification process. An earlier generation of PTI equipment, known as "Bookkeeper II," was being used by PTI when the Library's evaluation team initiated its examination of the Bookkeeper process over a year ago. Based upon results obtained with that earlier Bookkeeper equipment, the evaluation team concluded that the Bookkeeper process demonstrates the potential for meeting the Library's technical requirements for mass deacidification. The group indicated further that the process already meets many of the Library's specifications. The technical team also recommended that the Library work with PTI to enhance the Bookkeeper process.

While the evaluation team was drafting its observations about the results achieved by Bookkeeper processing and about subsequent accelerated aging and independent lab testing of materials treated with Bookkeeper II equipment, PTI and the Library pursued two important, complementary activities:

• PTI engineered and installed its new "Bookkeeper III" equipment, with a current capacity for treating up to 100,000 books per year and capable of being cloned to handle a greater volume; and
• The Library initiated a limited contract to treat 600 additional test books to assist PTI in addressing some of the issues that were being identified by the evaluation team.

In light of treatment results obtained with the Bookkeeper process, the Library presented Congress this month [December 1994] with a second deacidification Action Plan, consisting of two phases that will run concurrently for two years (1995-97), if the plan receives Congressional approval.

Phase A: A brief process enhancement initiative with the Bookkeeper process to be followed by a limited production effort. Over a two-year period, this demonstration contract would result in treating 72,000 books. The focus will be on achieving an improved product at lower cost. Since the Bookkeeper process does not impart odors or cause physical damages to treated materials, we expect to make rapid progress with process enhancement. We anticipate that most of this effort will be devoted to the limited production initiative, resulting in deacidification of actual books from the Library's permanent collections.

Phase B: The goal of this phase of the Action Plan, with guidelines to be announced in the Commerce Business Daily, is to encourage and evaluate other technologies that can demonstrate a potential to meet or exceed the Library's deacidification requirements (complete deacidification, adequate alkaline reserve, an increase in the life of paper by at least three times its normal expectancy) without damage to collections. The Library is also hopeful that, during this phase, a U.S.-based company will recognize the potential for commercialization of the DEZ technology and develop a facility for deacidifying books through this process.

The Library's proposed two-year plan reflects our determination to support the active development of mass deacidification technologies. We remain hopeful that our dedication to this effort, combined with mutual involvement by other like-minded institutions, will result in fulfilling the continuing interest of the library and archival communities in resolving one of our most pressing preservation challenges.

*"An Evaluation of the Bookkeeper Mass Deacidification Process." Technical Evaluation Team Report, for the Preservation Directorate, Library of Congress. Pittsburgh, PA, Oct. 1994.

"Mass Deacidification: An Initiative to Refine the Diethyl Zinc Process." Kenneth E. Harris and Chandru J. Shahani, Preservation Directorate, Library of Congress, Washington, DC. Oct. 1994. (The outline summary from this report is reprinted below.)

Summary of DEZ Report

In the summer of 1992, the U.S. Congress approved a Library of Congress (LC) Action Plan aimed at refining the diethyl zinc (DEZ) mass deacidification process and assisting in the development of other deacidification processes. This report deals with the DEZ phase of the two-year initiative. It describes the progress achieved in this effort and recommends changes that should be considered in any future application of the DEZ process.

Background:

• At the end of the procurement effort to obtain mass deacidification services in 1991, the expert advisory panel concluded that the DEZ process showed the greatest promise for meeting the Library's technical requirements.
• However, this process also had some unacceptable flaws:
  • Odor in treated books.
  • Iridescent rings on coated paper and covers and chemical attack on some book covers.
  • Adverse effect on adhesives and labels.

Objective of this project:

1. Minimize these remaining problems in no more than 12 runs in Akzo's pilot plant in Houston, Texas.

The developmental effort:

• Cause of odor a mystery since known chemistry cannot explain it. Several possible sources of odor formation investigated:
  • Impurities in diethyl zinc and the nitrogen gas used in the process
  • Degradation products present in paper
  • Air leaks in chamber
  • Tight or loose packing of books
  • Amount of alkaline reserve
  • Temperature in DEZ vaporization chamber
  • Temperature in reaction chamber
• Series of experiments in the Akzo plant and in the laboratory undertaken systematically ruled out all other possibilities for odor formation except the two temperature parameters.
• Lowering of these temperatures significantly lowered the extent of odor formation.
• About 4500 treated books stored in a room with no air circulation did not give off a noticeable odor. By contrast, 500 books treated for the procurement effort exuded a distinct odor.
• Chemical interaction between book covers and DEZ was also reduced at lower operational temperatures.
• Chemical attack on adhesives was also decreased at lower temperatures.

Operational difficulties:

• Inefficient plant design does not allow DEZ vaporization temperatures under 110°F.
• Minor modification to plant needed but impossible because of Akzo's decision to shut down the plant.

Optimal performance of Akzo pilot plant:

• Last two runs (numbered 11 and 12) employed optimum conditions to produce the best treatment that the Akzo plant, with its inherent limitations, was capable of producing in a consistent and reproducible manner.
• Achieved alkaline reserve of 2 to 3% calcium carbonate equivalents (LC's minimum requirement is 1.5%).
• There were no iridescent rings on glassy papers or chemical attack on book covers.
• Odor level was minimal.
• A management panel that examined books deacidified in these culminating runs found 98% of the covers and textblocks acceptable and 94% of the treated books to be free of unacceptable odors.

Conclusions:

• Odors and chemical attack on some book covers are caused by higher temperatures.
• Iridescent rings on coated papers and covers are eliminated by maintaining a high enough DEZ flow rate.
• Near-perfect treatment is achievable.
• Problems are resolvable with minor engineering changes.

DEZ Pros and Cons:

Main advantages:

• 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 papers, are thoroughly treated.
• Zinc oxide deposit in paper least likely to produce color shifts in inks and pigments since treated paper is almost at neutral point (pH barely above 7). Calcium and magnesium-based processes provide a much more basic (higher pH) environment and increase the possibility of color changes in images.
• A mature process which has been studied extensively for effectiveness; also extensive toxicology data available.

Disadvantages:

• Pyrophoric nature of DEZ needs good engineering, good safety practice and constant maintenance.
• A complex technology, for which engineers and other technical staff are needed 24 hours a day.
• Plant must be situated away from the library. Therefore, books need to be transported to and from the plant.
• Substantial capital outlay (5 to 10 millions) needed for a new plant.
• Economies of scale can only be achieved by building a plant with a substantial production capacity, necessitating a large capital outlay.

Other assessments of DEZ technology:

• Harry Ransom Humanities Research Center of the University of Texas recently concluded that ". . .it is now clear that the process works well for archives and manuscript materials."
• The General State Archives of the Netherlands determined this year that, of three processes studied for them bythe highly regrded TNO Centre for paper and Board Research in Inks do not run or bleed since no solvent is employed. This would be an essential requirement for treatment of archival manuscripts, but printed inks in books are less vulnerable.
• the Netherlands, DEZ is best suited for the treatment of archival materials and manuscripts.
• A. Liénardy in Restaurator in 1994 (Vol. 15, No. 1, p. 1) found DEZ and Bookkeeper to be the two most promising technologies among seven mass deacidification processes compared.

Future possibilities:

• Library needs to decide whether to invest heavily in a new DEZ plant at this time or to keep its options open for the future.
• Mass deacidification is a technology that has not yet matured to its fullest extent. Therefore, continue to encourage the development of such technologies.