The Abbey Newsletter

Volume 16, Number 7-8
Dec 1992

DEZ Mass Treatment: Testing for Compliance to Specifications

by Scott Kellar

Northwestern University Library recently initiated a contract with Akzo Corporation to treat approximately 3,000 volumes with the diethyl zinc (DEZ) mass deacidification process over the period of a year. We are currently selecting scores from our music collection for treatment. Our selection process presently includes all printed materials except items on coated paper, brittle material, bindings with clear film lamination, and books printed on alkaline paper, labeled as conforming to ANSI standard Z39.48-1984.

Our quality control begins with a physical inspection of all treated items immediately after their return. A checklist of fourteen possible observable side effects (odor, loose call number labels, etc.) is used to monitor both minor and serious problems. New call number labels and rebinding, if necessary, are handled at that point through the Materials Processing unit of our department. After this inspection, quality control is handed over to the Conservation Lab.

As Collections Conservator, it is my responsibility to deermine whether the minimum treatment specifications of our contract are being met for each shipment. Our contract's specifications for treatment, modeled after those required in the Library of Congress RFP [request for proposals] for mass deacidification, state that the paper will have a minimum pH of 6.7* and a minimum zinc oxide content (alkaline reserve) of 1.0%. Our contract further states that compliance with these specifications may be determined by either the vendor or the client through an analysis of paper samples treated along with Northwestern's materials.

In order to participate in this area of quality control, we are currently approaching the compliance testing challenge on two levels. On one level we are doing quick, routine testing of 10% of each shipment, in batches that could range from 30 to 170 items. This testing broadly verifies that the material has been treated completely. On the second level we are doing careful chemical analysis of the paper samples that we insert in volumes to receive treatment.

For the randomly selected 10% test group, we are performing two tests. A student assistant does a simple spot test of each volume with chlorophenol red (Abbey pH Pen) on the inner margin of a page at the center of each volume. If the spot is purple then the book is considered deacidified. The student then goes through them again, scanning each volume (open to a page at the center) with a long-wave UV lamp. The UV light scan reflects the zinc oxide as a faint orange glow and shows up any areas the DEZ gas did not penetrate, leaving a circular area that is clearly defined in the center/gutter area of the book. If no untreated areas are evident, the volume is considered to be uniformly treated.

In making a chemical analysis of the inserted sample papers, we are looking for both pH and alkaline reserve (measured as zinc oxide content). The sample paper is necessary, as the testing is destructive and cannot be performed on collection material. Clear Spring Offset (an unbuffered, uncoated printing paper made by Westvaco, Inc.) is specified in the contract in order that both client and vendor will be testing the same type of sample paper, eliminating unnecessary discrepancies in results. Our current procedure is to insert a sample into the centers of five randomly selected volumes for each shipment to be treated. Of these samples, all five are tested for pH and three are also tested for alkaline reserve.

The procedure that we are using to test for compliance at this level is the procedure developed by the Library of Congress for testing the effectiveness of the DEZ process. This procedure (named JA-805) is reproducible in a library conservation lab with chemical supplies and equipment that are normally available from university chemical supply rooms or major chemical suppliers. The procedure requires that the treated test paper be made into a slurry that is subsequently tested for pH with a pH meter. Following this, a titration is performed to ascertain the amount, by weight, of zinc oxide present. (Note: As the molecular weight of zinc oxide is less than that of calcium carbonate, it is necessary to multiply the zinc oxide content by 1.24 in order to find the calcium carbonate equivalent [CCE].)

Here is a recent report, giving our results:



RETURNED 11/1/92

10% Test Sample:
pH pen test results:  All positive
UV light test results:  All positive


Five Clear Spring Offset sample results:

                #1      #2      #3      #4      #5
                --      --      --      --      --
           pH  7.0     7.0     7.1     7.0    7.1
  ZnO content 1.19%   1.00%   1.38%

All tests meet the minimum requirements.

Test results are considered satisfactory if:

1. The 10% test sample for completeness of treatment all test positive.

2. Destructive testing of Clear Spring Offset samples indicates a minimum pH of 6.7 and zinc oxide content of 1.0%.

The results noted above indicate that this particular shipment complies with the specifications set forth in our contract. If a significant deviation should occur in future shipments, further tests might be performed by both parties and a discussion begun toward resolving the problem.

Our Preservation Department has taken this step in quality control in order to be consistent with our policy in all of our vendor-provided programs, including preservation microfilming, preservation photocopying, library binding, and the purchasing of archival products for both the conservation lab and for general library use. Experience has taught us that taking this responsibility seriously, for both old and new products and services, is necessary to assure consistent high quality.

*Unlike calcium and magnesium carbonate, zinc oxide in a dry state has a pH slightly below 7. This does not, however, affect its ability to neutralize acids. A further benefit of this fact is that it does not adversely affect material with pH sensitive dyes and colors during treatment.

 [Contents]  [Search]  [Abbey]

[Search all CoOL documents]