The Alkaline Paper Advocate

Volume 06, Number 1
Jun 1993

Revised ANSI Standard Published

The first revision of the well-known paper permanence standard, ANSI /NISO Z39.48-1984, has appeared, improved and with expanded coverage. It gives us a standard that applies to coated as well as to uncoated paper and to documents as well as to printed materials. It makes up seven pages of a 22page 7" x 10" booklet, sold for $20 plus postage by NISO, from their fulfillment office at PO Box 1272, Alexandria, VA 22313 (1-800/282-NISO). (NISO is establishing its own publication program as of August 6,1993.) The bibliographical reference is:

American National Standard for Permanence of Paper for Publications and Documents in Libraries and Archives: ANSI/NISO Z39.48-1992. (National Information Standards Series, ISSN 1041-5653). Transaction Publishers, New Brunswick, 1993 (©1992). ISBN 0-88738-932-5.

This revision of Z39.48 is more sophisticated than the original standard, with more attention being paid to test methods. Fold endurance has been dropped, so tear resistance is the only measure of strength called for. This is expressed as the "tear index," in n-millinewtons of force divided by paper weight in grams per square meter. It works out to the same tear resistance as in the 1984 edition, but now a single figure can be given for all weights. The tear index for coated paper (3.50) is necessarily lower than that for uncoated paper (5.25).

Minimum pH for uncoated paper is 7.5 and minimum alkaline reserve is 2%, just as in the 1984 edition. Coated paper base stock can be as low as pH 7.0 if the paper as a whole meets the alkaline reserve requirement.

Instead of "no groundwood or unbleached pulp," the standard calls for a maximum lignin content of 1% (kappa number 7). In view of the many pulping methods that use both chemical and mechanical (grinding) processes, and the fact that some bleaching methods do not remove very much lignin, this new focus on quantifiable levels of lignin is an improvement.

There is a note saying, "Testing has shown that some papers with higher lignin levels which otherwise meet the requirements of this standard can exhibit excellent retention of physical strength after accelerated aging." Strictly speaking, this statement is true, but the same could have been said about papers with low pH, low tear resistance, or low alkaline reserve. Some papers are survivors: they test well and survive through time, standards or no standards. Similarly, some papers that qualify in every respect will not test well or survive through time, because they have faults or weaknesses not ruled out by the standard. This is because paper is a complex substance, and standards cannot cover all factors. Also, when new factors are introduced, such as the inclusion of mechanical pulp and calcium carbonate in the same paper, it takes time for research to evaluate the effect on permanence.

For more information about this and other NISO standards, write NISO, PO Box 1056, Bethesda, MD 20827.

Test Methods, Formal and Informal

The test methods specified in any standard, if they are accurate and appropriate, are important in three ways: 1) they help the buyer and seller communicate, especially if both parties have ready access to the published methods, 2) they put power in the hands of any consumer willing and able to use the test methods specified, by enabling them to monitor the quality of goods received, and 3) they protect the supplier from arbitrary, ambiguous, conflicting or shifting demands in the marketplace.

Some of the tests called for in this and other standards are necessarily complex. Buyers without a staff chemist and the proper test equipment have to either send samples out to a commercial lab for testing (which is expensive), or ask the manufacturer whether the shipment complies with the standard.

In addition, there are things that cannot be tested for, such as whether an alkaline process was used to make the paper. The ANSI standard explicitly allows acceptance of the manufacturer's certification of 1) the core paper pH and of 2) the use of an alkaline process in its manufacture. As a way of confirming the manufacturer's figure for pH of the core paper, it also suggests two do-it-yourself methods: delaminating the paper and taking the surface pH with a meter, or using a pH indicator such as chlorophenol red solution on the core surface. This suggestion will be helpful to users.

Unfortunately, there are no satisfactory do-it-yourself methods for testing alkaline reserve or tear resistance. The spot tests for lignin, using phloroglucinol or other indicators, are useful but only approximate.

Other Standards Waiting in the Wings

The new ISO standard should be out in 1994, at latest, because it is in the last stages of balloting. If all goes well, the revisions of the four ASTM standards should appear soon also.

ASTM's Committee D 06.20 has also been working for the last six years on a "Standard Guide for the Selection of Permanent and Durable Offset and Book Papers," which like the ANSI standard will cover both coated and uncoated papers. In draft it is 25 pages long, including five tables of test data (before and after aging) on contemporary papers in the marketplace, a bibliography, and a great deal of background information on permanence and aging.

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Timestamp: Sunday, 03-Mar-2013 21:42:12 PST
Retrieved: Sunday, 19-Nov-2017 12:34:14 GMT