Volume 06, Number 1
Jun 1993

Letter

We are providing space in this issue for William Hollinger, President of CRI, to respond directly to readers regarding my review of Conservation Resources International's "Specifications for Archival Papers" (Alkaline Paper Advocate, December 1992, v.5 #6, p. 46-47).

I would like to emphasize that I was not referring to the company's products or to the company in general. I believe Conservation Resources International (CRI) deserves its good reputation for high quality archival products, formulated to meet the requirements of the most sophisticated institutional customers for their conservation programs.

Ellen McCrady, Editor

To the Editor:

This is our response to the review of our catalog in the December 1992 Alkaline Paper Advocate, published in May 1993. To keep our response to manageable length, we will focus on points that have some practical significance for archival quality. It is important to understand just how strong archival paper can be made in terms of folding strength, and it is useful to know that there are ways to employ deceptive practices when making archival paper. An example is the inappropriate use of alum-rosin sizing, as discussed below. We have italicized the comments made by the Alkaline Paper Advocate, and our response follows the italics.

The review says, "spot tests, which are relied upon by most consumers, do not discriminate between various low levels of lignin. "

We not only do not use this "spot" test (the phloroglucinol [1,3,5-trihydroxybenzene test]), we counsel against using this test on the very same pages the review criticizes. The phloroglucinol test is positive with lignin compounds containing Coniferyl aldehyde end groups. This negative condition makes the phloroglucinol test of no value when evaluating materials made from chemical wood pulps that are fully bleached (a minimum standard for pulps used in CRI products).

The review says, "if the pH of a paper is above 8.5 you can't size with alum and rosin anyhow. Why even mention it? Perhaps this was an attempt to impress those librarians who may know about alum and rosin but are vague about pH."

The following information was contained in an intra-company memo we sent in August 1990. It was meant as a warning to our employees, and we did not publicize this information, because we did not want to make it available to people who might be tempted to capitalize on it. A quotation from this memo follows:

"Alum/rosin [acid] sizing. Alum/rosin sizing used to be ineffective above pH 5.5. People make a regular acid, alum/ rosin sized sheet, then put something like sodium bicarbonate in the sizing press to make a very alkaline solution. The result is an acid sheet with an acid core that has a very alkaline surface. The 'trick' is in the nature of the pH test. Since the paper is all ground up in water and the pH read from the resulting slurry, the pH reading you are getting is an average and will be appropriate for an 'archival' paper. In reality it is something quite different. Not only is the paper acidic, the sizing will eventually disappear leaving a paper similar to blotting paper. To test: the only way to test is to split the paper into layers and test the pH of the center and surface separately. To split the paper, use a sharp tool like a knitting needle and start the separation at the edges. 0.010 should be fairly easy to do, and with practice you should be able to do 0.006 papers.

"The second way to make paper 'acid free' with acid (alum/rosin) sizing is to use a newly developed alum/rosin sizing that can be used at a pH of 7 to 7.3. The development of this is, in my opinion, analogous to the discovery of a more efficient way to kill whales."

The review says, "the high pH of today's paper and board is an accidental side effect of calcium carbonate manufacture anyhow, not an intended characteristic of the paper. "

It is not accidental in our paper. As long as we are on the subject, let's look at some alkaline buffers, and detail the advantages of each of them. MgCO₃ and CaCO₃ can both be used as a buffer meant to prevent acid from penetrating paper. The molecular weights differ between these two compounds; note the mass of each that is capable of reacting with one mole of acid (49 grams of pure sulfuric acid): 42 grams Of MgCO₃ and 50 grams of CaCO₃. This means that it only takes 42 grams Of MgCO₃ to neutralize 49 grams of H₂SO₄, while 50 grams of CaCO₃ would be required to neutralize this much acid, and therefore you get greater effectiveness, or higher efficiency, from a given amount of MgCO₃. However, of the salts which form after these buffers have reacted with acids, calcium salts may be more desirable because they are less apt to pick up moisture and move in the paper to a point where they might be abrasive. These are reasons to use both CaCO₃ and MgCO₃.

Both calcium carbonate and magnesium carbonate are effective in reacting with acids in the paper. Compounds formed include calcium sulfate (from reacting with sulfate, sulfate, or sulfur oxide gases) commonly encountered as gypsum or plaster of paris, and magnesium sulfate (produced from the same sources as calcium sulfate) and commonly encountered as epsom salts. Both calcium and magnesium form stable salts with organic acids, although the calcium salts are typically more stable (less soluble) than are the magnesium salts. (another reason for having some CaCO₃.) The magnesium salts may be more likely to pick up moisture, and move to the surface where they may pose an abrasive problem. However, a given amount of magnesium will offer more potential to neutralize acids present than will the same quantity of calcium.

There are specific reasons to use alkaline buffers. I hope we have convinced you the use of alkaline reserve in our paper isn't an "accidental side effect." In fact, we have applied for world-wide patents which encompass the use of new buffering technology.

5. Abrasion test. "results are supposed to be reported not in percent of fibers lost, but in milligrams/ 1000 revolutions."

The Library of Congress specifications also call for the fiber loss to be given as a percentage of the total weight. Milligrams/1000 revolutions converts directly to percent of fibers lost, which is meaningful to people who are not paper chemists. If two percent of the fibers are lost, most of us can easily grasp that concept.

6. Smoothness test. The review says, "Sheffield smoothness is T 538 om-88. 'UM' is not an abbreviation used either now or in the past by TAPPI. There is no test method numbered 518. Smoothness is not a measure of strength."

UM stands for "useful method" and we have a book,

TAPPI USEFUL METHODS 1991, which lists "UM 518 Smoothness of paper (Sheffield)." The ISBN number of this book is 0-89852-206-4. As to the charge that the smoothness test doesn't measure strength, let me offer this. Permanent/Durable used to be inseparable when used to describe an archival conservation paper. Over the years the durable part fell by the wayside as the quest to meet the lowest specifications with the lowest possible cost paper became the focus of some companies. We try to retain these values of durability because we feel they are a very important part of the specifications for permanent paper. Smoothness is a physical test, it has an effect on durability, and this is why it is listed under this portion of our specifications.

7. Folding endurance test: The review says, "Conditioning is covered in T 402, not T 51 1; the fold test is T 511. " Our specifications call for the paper to be conditioned, and the folds tested under T 511. In T 511 om 88, "conditioning" is the heading of section 7, where it says "condition and test the paper in an atmosphere in accordance with TAPPI 402." These are the procedures we use.

Then the review says, "T 511 calls for results to be reported as the log of the fold number, not directly as the fold number." Under T 511, section 9.2, reporting the actual number of double folds for machine direction and cross direction is permitted. So that is what we do, because people are used to it, and because it is easier and more readily understood than logarithms.

A complaint is lodged against the number of folds we get from our paper. The review says, "A fold number of 1000 is extremely high, about 35 times higher than what the ANSI/NISO paper permanence standard calls for."

1000 folds really isn't all that high if you choose the right fibers and paper making technology. The Library of Congress specifications now call for a "minimum fold endurance of 1000 double folds in the weakest direction with a 1 kg load." 2000 folds is not unusual, and 3000 to 4000 folds can be achieved. One thousand folds is 35 times higher than 28.6 folds. We do not consider a paper "permanent" which will only withstand 28 folds. The definition of a totally deteriorated paper has been given as having 1 fold left at 1/2 kg load. It should be clear that an alkaline paper which withstands 1000 folds in the weakest direction at a 1 kg load will last longer than one which withstands only 28 folds.

The reality is that the strength and durability characteristics of our papers are very important. This was illustrated recently during tests run by a U.S. Government testing facility. Our high quality 0.010" Lig-free® type I paper kept S0₂ at bay over three times longer than the six times thicker (0.060") cheap tan "low lignin" and gray archival box boards. The diffusion through our thicker 0.040" and 0.060" boxboards, if any, was too low to measure. These test results are presented in the Spring 1993 AIC Journal.

9. Stiffness test: The review finds the following faults: "Stiffness is not normally used as a strength measure. It should be T 489, not TAPPI 489. Results are not supposed to be reported in 'stiffness units' but either in gram centimeter values or in millinewton meters." The Library of Congress specifications also call for the results of this test to be reported in "stiffness units." In the paper industry, T means TAPPI, and TAPPI means T. I find it difficult to believe this confuses anyone. As to the strength issue, it is our practice to use stiffness as a form of strength. Stiffness relates directly to modulus, and papermakers can combine stiffness and air porosity as an indicator of refining.

10. Bursting strength: The complaint here is, "TAPPI T 807 is for paperboard and linerboard, not for paper. Bursting strength of paper is measured with Test Method T 403. " True, but the basic difference between these tests, one for paper, the other for board, is in the range of the gauge which measures the bursting strength. The T 403 paper bursting range is 75 to 225, and the maximum reading of the gauge used in T 403 is 300. Therefore the bursting test on our paper must be done under T 807, where the gauge reads the range our papers fall into.

12. Fading test: The review again says, "There is no test method called Tappi UM-461. There is a method numbered T 461, but it is for flame resistance. " There is a test TAPPI UM 46 1. It is in TAPPI USEFUL METHODS 1991 (ISBN 089852-206-4). It is listed as "TAPPI UM 461 Fading resistance of paper and paperboard." The Library of Congress standards also call for TAPPI UM 461.

Under Photographic/Textile Conservation Paper, the review doesn't detail specific complaints. It says, "This section contains the same sort of errors as the previous one. It cites one superseded test method, one method since revised, and one non-existent method. "

The test methods are also valid in this section. Previous discussions lead me to believe the "non-existent method" is the T. J. Collings and F. J. Young Silver Tarnish Test, which does exist, and which was published in Studies in Conservation, 21 (1976), 79-8, the Journal of International Institute of Conservation (otherwise known as IIC).

I personally know of one very significant contribution this test made to the field of conservation. There was a time, many years ago, when a certain conservation paper was widely used to make photographic negative envelopes. This paper was not made or intended for photographic use by the paper mill which produced it, but it was adapted for this purpose by several companies because it was readily available in small quantities. This test was used to discover Sulfur in the paper, and people subsequently stopped using it for photographic storage, thereby preventing a great deal of potential damage.

I hope that everyone reading this will realize that our most important asset is our reputation. We work very hard to produce materials of the highest quality. We were the first company to make a gray/white board which contained alkaline buffering distributed evenly throughout the sheet, including the center plies. We made the first lignin-free board, and developed our Lig-free® type II, a combination of buffered and non-buffered board to answer the needs of photographic curators and others who were concerned about the effect of alkalinity on their collections. We have now developed MicroChamber^TM papers and boards, the first conservation materials available which actively protect your collections. We spend our money on research and development rather than marketing, and we rely on your faith in our integrity and the quality of our products for our continued existence.

Sincerely yours,