Selections from North American Permanent Papers
Ellen McCrady <firstname.lastname@example.org>
Cultural institutions buy large amounts of paper at a time for various purposes including storage of their collections, and they generally have a laboratory equipped and staffed to test it for permanence, to see if they have received the kind of paper they ordered. (Discrepancies are not uncommon.) Individuals and small organizations, however, cannot afford their own labs, so if they are interested in permanence, they have to seek alternatives, like buying North American Permanent Papers. But NAPP will not always be able to give them the information they need, although it covers a large number of papers on the market. It is not complete, to start with; it will become obsolete in time; and there is no way it can help anyone to evaluate that pile of blank office paper or box of endsheets that may have been bought before 1980.
Sending samples out to a commercial lab is not always an option for them, because testing labs may charge $300 to $350 to do the required four tests on a single paper. With fewer resources at their command, the small customer often has to do spot tests, improvise equipment, and use approximations of the official methods. There is nothing wrong with these do-it-yourself measures, as long as a few professional precautions are taken, and as long as the results are seen as indications rather than accurate measurements.
pH. Although pH is the only property in the ANSI/NISO standard that can be easily tested by untrained people, fortunately it is one of the biggest factors in permanence. A fairly good idea of pH can be given by pH indicator solutions or test papers. Even papers advertised as "acid free" should be tested for pH now and then, because discrepancies do occur. Sometimes books are published with a notice that the paper meets the requirements of the ANSI/NISO standard, but when tested with a pH indicator they turn out to be acid. Everyone who surveys the pH of library books has found some of these anomalies. And copy paper sold in boxes marked "acid free" may be acid. I know of two instances in which paper described as alkaline was sold to a university for use in letterhead and archival documents turned out to be an acid paper with the same watermark!
I don't think deliberate deception is often involved in the substitution of acid paper for alkaline. Ignorance, yes; underestimation of the customer's sophistication, yes; deception, no. There are too many occasions when a slipup might occur, starting at the mill. We sell a lot of pH pens to paper mills for marking rolls of paper in their warehouse; they obviously need the pens because otherwise they can't tell acid from alkaline. If they don't use pH pens, the wrong paper could be shipped to the converter or directly to the customer.
Another example: The publisher's print shop might not have been able to get the kind of paper they wanted, so at the last minute they had to take what they could get. (Print shops take publishing deadlines very seriously.)
Paper sold in labelled boxes, like that acidic copy paper in a box labelled "acid free," was probably cut and packaged by a converting company had not yet devised a way of keeping acidic paper separate from alkaline paper.
The paper mill may have several machines, which make either alkaline or acid paper (a common arrangement, especially for a mill that is converting its machines to alkaline one at a time). Sometimes one or more machines may switch back and forth between acid and alkaline. For practical reasons, perhaps that day the paper in question had to be made on another machine, which normally ran acid, and things got mixed up. Or the merchant wants to use up the old stock before reordering from the mill, and is unaware that the old stock is all acid. Or the mill went back to the acid process because of production difficulties, and had no way of alerting all its customers. None of these mistakes is easy to catch, but when a mistake is made, the consequences for permanence are likely to be serious, if the customer does not spot the mistake before it is too late.
Alkaline reserve. Nearly all alkaline paper contains calcium carbonate as a filler. The average paper contains at least 2% and occasionally as much as 30% filler by weight. The standard requires only 2%. This calcium carbonate, an alkaline reserve, keeps the pH of paper and board from declining as time goes on. Even alkaline papers will eventually become acidic, without an alkaline reserve.
There is no easy way to measure alkaline reserve outside the lab, but the easiest way is actually the one called for by the ANSI/NISO standard: ASTM D 4988-96. This standard can be ordered separately from ASTM. Some instruction from a technical person is probably necessary. It takes some simple lab glassware, distilled or deionized water, some methyl red and 0.1 N solutions of HCl and NaOH. The method involves defibering the paper and dissolving the alkaline salt with a measured amount of dilute acid, then back-titrating with a dilute alkali until a pH indicator changes color.
Lignin. The easiest spot test for lignin uses phloroglucinol solution, which can detect lignified fibers in amounts as low as 5%. It indicates percentages above that by changing from pink to red to brilliant magenta for newsprint and other groundwood. It must be handled with care, because up to 50% of the phloroglucinol indicator is concentrated HCl. The solution is very sensitive to light and heat, so it has to be kept in a black bottle in the refrigerator and replaced periodically. It can be purchased from Integrated Paper Services (IPS), the Institute of Paper Science and Technology (IPST), and TALAS.
William J. Barrow (who demonstrated the role of acidic sizing in deterioration of library books) popularized the use of phloroglucinol with his little spot test kit, which is no longer produced. Most users, however, rely on the manufacturer's statements about lignin content. Perhaps the simplest option of all is to test for light-induced yellowing, as described below, because most yellowing is caused by lignin.
Light-induced yellowing of paper can be easily and systematically observed by mounting a row of test papers on a card and putting them in a sunny window, with half of the row covered snugly by tinfoil or other opaque material. The covered half of each paper serves as a control. Changes can be observed by lifting the tinfoil. This kind of aging can continue for weeks, months or years, as long as the observer is interested, but results should show up in a matter of days.
Tear resistance. This not hard to measure, if you have the equipment to do it with, but few people have the equipment. There is no simple version of the tear test that can be performed without equipment, so small customers have few options. One option that can be used in many situations is to compare the paper under consideration with one that has a known tear strength. Simply tear each by hand, first in the machine direction, and compare the force it took for each; then in the cross direction, and compare. The same can be done to find a primitive burst strength (by pushing a thumbnail through the paper) or folding endurance (by folding a corner back and forth until the paper fails).
Condition surveys of library collections often use the corner fold, rather than a tear test, because results can be quantified and the test is easy to do in the stacks: A page corner is folded back and forth with the fingers until it breaks. Two or four double folds are often used as the criterion for "brittle." Such surveys have now been done in so many countries that it is possible to say that a third to a half of books in American libraries are brittle, while in Europe the proportion is only about half that.
Accelerated aging to estimate general permanence. The process itself has been described in the section entitled "The Nature of Permanence." Standards for aging with dry and moist heat are in the ASTM book of standards (D 776 and D 4714). D 5634 (Standard Guide for Selection of Permanent and Durable Offset and Book Papers), for instance, uses the method described in D 4714, and recommends that papers required to last 1000 years be aged at 90°C and 50% RH. It recommends seven different tests of strength that can be used before and after aging, and discusses the extent to which their results change during accelerated aging. (Tensile strength, for instance, changes very little, while fold endurance is quite sensitive.) Several tables in an appendix to this standard guide give data on retention of properties in acid and alkaline papers aged for 12 days. This data comes from testing done by both ASTM and NISO when they revised their standards, so that they could be sure their specifications were reasonable and effective.
TAPPI's test methods for dry and moist aging, T 453 and T 544, closely parallel the ASTM standards. TAPPI has no guide for selection of permanent paper like ASTM's.
One way to age paper at home is to bake it in the oven at about 195° F, with a pan of water to provide humidity, for a few days. As with all these do-it-yourself test methods, a paper of known characteristics should be included for comparison, but not right next to the other paper, and the results should be considered approximate.
Aging can be speeded up considerably by aging in airtight enclosures. Test tubes, polyester encapsulations, and other inert enclosures may be used. This method has not been correlated yet with standard methods, but it shows promise.Ellen McCrady
American Institute for Conservation. Paper Conservation Catalog, Chapter 10, "Spot Tests." 80 pp. Chapters can be ordered individually for a modest price from AIC, 1717 K St., NW, Suite 301, Washington, DC 20006 (202/452-9545, fax 452-9328). This gives more information than the TAPPI Test Methods volume.
American National Standard for Permanence of Paper for Publications and Documents in Libraries and Archives (ANSI/NISO Z39.48-1992). National Information Standards Organization, Bethesda, MD, 1992. $24 from NISO Press Fulfillment, PO Box 338, Oxon Hill, MD 20750-0338 (800/282-6476; fax 301/567-9553).
ASTM. 1997 Annual Book of ASTM Standards, volume 15.09. ASTM, 100 Barr Harbor Drive, West Conshohocken, PA 19428 (610/832-9500, fax 610/832-9555). Publication code # (PCN): 01-150997-11. 1403 pp. This volume includes all of ASTM's paper permanence standards, including the four revised in 1994 and the two new standard guides; also tests and standards for every conceivable property of paper.
Clapp, Verner. "The Story of Permanent/Durable Book-Paper 1115-1970." Scholarly Publishing 2 (1971): 107-124, 229-245, 353-367. Reprinted under the same title, in Restaurator Supplement 3, 1972. 51 pp. A classic, very well researched and written; includes an accurate and comprehensive summary of Barrow's research.
Feller, Robert L. Accelerated Aging: Photochemical and Thermal Aspects. Getty Conservation Institute, Santa Monica, CA (now in Los Angeles) . (Research in Conservation 4) 277 pp. $33 postpaid from Getty Trust Publications (800/223-3431). This has been described as "the best source of information on the subject you can buy anywhere, anytime, at any cost." There is a 57-page bibliography and a 12-page index. The volume does not cover every aspect of accelerated aging, but it covers the two most common methods used.
Spot Testing for Unstable Modern Book and Record Papers. W.J. Barrow Research Laboratory, Inc., Richmond, VA 1969. (Permanence/Durability of the Book VI) 28 pages. Now out of print. Describes spot testing for groundwood, acidity, alum and rosin. The lab closed about ten years after this booklet was published.
TAPPI Test Methods 1996-1997. Test Method T 401 om-93, Fiber Analysis of Paper and Paperboard. Preparation, use and interpretation of spot tests for fiber analysis are in Appendix E-G to this test method; stains for groundwood are in Appendix F.
American National Standards Institute (ANSI) (p--Distributes ISO standards in the U.S.)
11 West 42nd St., New York, NY 10036 (212/642-4900)
Chicago Paper Testing Lab (t)
3356 Commercial Ave., Northbrook, IL 60062 (708/480-1670)
Institute of Paper Science & Technology (t, i)
500 10th St. NW, Atlanta, GA 30318 (404/853-9500, Fax 853-9510)
Integrated Paper Services (i)
101 W. Edison Ave., Suite 250, PO Box 446, Appleton, WI 54912-0446 (414/749-3040, Fax 749-3046)
NISO Press Fulfillment (p)
PO Box 338, Oxon Hill, MD 20750-0338 (800/282-6746, Fax 301/567-9553)
568 Broadway, New York, NY 10012-3225 (212/219-0770, Fax 212/219-0735)
Technology Park/Atlanta, PO Box 105113, Atlanta, GA 30348-5113 (800/332-8686, Fax 770-446-1400)
U.S. Testing Service, Paper & Packaging Film Dept. (t)
291 Fairfield Ave., Fairfield, NJ 07004