Volume 17, Number 2
Sep 1993

Letters

To the Editor:

The Preservation Directorate is pleased to announce that it is once again distributing black and blue manuscript marking ink, free of charge, and has revised the existing Preservation Leaflet No. 4 into "Ownership Marking of Paper-Based Materials." We are very pleased with this new publication because we feel it more adequately addresses some issues of security, and provides a practical guide to the application of the ink. We are delighted to be able to distribute the ink again throughout the preservation community and to meet a growing need in the field. Security of collections continues to be a major preservation concern and once again the Library of Congress Preservation Directorate is proud to be a part of the solution.

To the Editor:

Robert Milevski's letter in the last issue concerning my article on DEZ compliance testing definitely merits a comment or two. I fully agree that my particular piece of information, by itself, is "incomplete and inconclusive," which is why forums for information dissemination (and discussion), such as the Abbey Newsletter, exist. In submitting "DEZ Mass Treatment: Testing for Compliance to Specifications," I have added yet one more piece to the pool of information to which Robert has certainly been a contributor.

It was, and is, my hope that by describing testing methods that can be performed in the average conservation lab, library conservators would be challenged not only to examine the visible effects of DEZ treatment on library material, but also to examine the invisible effects. Damage to binding components is immediately self-evident and quantifiable; pH and completeness of treatment are not. Compliance testing is but one more tool for preservation administrators and conservators to use in weighing the pros and cons of a mass deacidification process.

Damage to binding components, a special interest of Robert's, was not within the scope of my article, as is hopefully apparent. There have been some interesting articles and papers presented on this aspect of the process, as interested conservators are well aware of by now. Northwestern's own experience in observing negative visible effects of DEZ treatment on library material is thoroughly covered in Mass Deacidification: A Report to the Library Directors (CIC), submitted by the CIC Task Force on Mass Deacidification in April 1992 (available from CIC*).

Robert appears to believe that the point of my article was to show that Akzo can comply with NUL contract specifications. The point rather is that it is possible for the average institution to verify whether the vendor can comply with or exceed an agreed-upon specification, shipment by shipment.

Ultimately, opinion on processes such as DEZ must be reached and acted upon by each institution. During the process of forming those opinions it is, I believe, very important to remain as objective as possible in order to observe and weigh each factor in the clearest possible light. It was for this purpose and with this perspective that I submitted the information found in my article. I hope that Robert will reread it and discover that the expressed intent and information given is well within this spirit.

* Committee for Institutional Cooperation, 302 E. John St.,
Suite 1705, Champaign, IL
61820 (217/333-8475).

To the Editor:

Re: "ISO Responds to Claims that Lignin is Harmless"
The Abbey Newsletter, December 1992

Your efforts to interpret and communicate issues to the community served by your newsletter are applauded. The complexity of the permanent paper issue demands that we do all we can to improve the understanding of interested, even non-interested parties.

With the latter thought in mind I wish to offer a few points designed to clarify and/or correct the subject article. We trust that you will find this added input of sufficient value to merit inclusion in a future issue of the Newsletter.

Chemi-thermo mechanical pulp (CTMP) is, as you stated, a relatively new kind of high-yield pulp. "High yield" refers to those pulps which give a high yield proportion of pulp for the amount of raw material fiber put into the process. Typically, high yield pulps return 85 to 95% pulp, or yield, to the raw material fiber. Most CTMP pulps have a yield in the high 80s to low 90s percent range. Bleached chemical pulps have yields of less than 50%.

The major factor influencing yield is lignin. In bleached chemical pulps the lignin is chemically dissolved away, leaving pure cellulosic fiber, whereas in CTMP and other high yield pulps, the lignin is largely retained in the pulp product.

The table below shows comparative lignin contents for newsprint and CTMP-containing "fine papers." Note that the lignin content of hardwood (aspen) CTMP is in the 16 to 18% range, significantly lower than the approx. 28% level found in traditional softwood mechanical pulp.

Note too, that newsprint contains up to 100% mechanical pulp, whereas the CTMP-containing papers that were tested by NISO (during the development of the ANSI Z39.48 standard revision) contained from 8 to 34% aspec CTMP. Thus the total lignin content of the CTMP-containing sheets being promoted, which have passed the long-term aging tests for permanent paper use, is actually only 1.5 to 6.5% lignin.

In commercial paper grades it is likely that CTMP would be used in the 8-20% (of the total paper weight) range, giving lignin levels in the range of 1.6 to 4%--substantially less than the 25 to 28% found in newsprint. This point is extremely important to recognize since a number of the "opponents" to the use of lignin have a perception that all lignin-containing papers perform like newsprint--this is not the case. As a consequence, the tendency for CTMP papers to yellow resulting from ultraviolet light exposure is substantially less than the levels commonly perceived or experienced with groundwood papers and newsprint. Also, although there is currently no scientific evidence to prove it, if it should subsequently be discovered that there is a negative effect from lignin on paper permanence, it is unlikely that lignin levels below 4% will have any significant impact.

Your article states that "CTMP. . . can be used to make paper of apparently high quality, provided it is filled with calcium carbonate to whiten it and stabilize it chemically." Since the large majority of coated and uncoated papers in North America are now made in alkaline systems, calcium carbonate, of various kinds, is the filler of choice. In CTMP-containing papers the carbonate is not used specifically to whiten the paper. There is also no specific chemical instability that needs to be stabilized. Aspen BCTMP (as pulp) for printing and writing papers is available at up to 87 GE brightness, compared to 88-90+ for chemical pulps. (Note that the newer TCF, totally chlorine-free, kraft pulps can range from low 80s to 86 brightness.) Uncoated papers for offset printing and photocopying are usually in the 80-87 brightness range, usually "dyed-back" (black dye introduced), to reduce the brightness. BCTMP aspen pulp has proven to provide adequate brightness and stability for printing papers.

CTMP technology was developed in Scandinavia to better utilize their limited forest resources. Its use in Canada is not specifically in response to any "growing shortage of trees," although it is true that a world-scale CTMP mill requires approximately 25% of the forest resource needed to support a viable-scale chemical pulp mill.

You mention that the CTMP "pulp mills are hurting not only from the recession, but from an unexpectedly low demand for their product. They have to export or die." It is true that they are suffering from the effects of global reduction in pulp and paper demand and slump in all pulp prices. It's well known that the whole pulp and paper industry is suffering. However, the fact is that demand for CTMP has provided a better operating rate for the CTMP producers than most chemical pulp mills have experienced.

CTMP users in Europe and the Pacific Rim have found distinctive value in CTMP pulp and have continued to buy it despite a contraction, even overlap, in the price differential versus chemical pulp. To date these markets have been less restricted by standards and are large purchasers of market pulps.

The lobbying, in the U.S. and Canada, against various standards which discriminate against lignin has been necessary since there is so much misinformation and misunderstanding around lignin and the potential for CTMP-containing papers. It has been shown already that there is no scientific evidence to support the allowance nor the limitation. A maximum lignin level of 3% would permit up to 20% aspen CTMP to be used in a paper containing 17% filler. There is no reason to believe this would have any deleterious effect on paper permanence.

I apologize for the length of this letter, but you raised a number of points which we felt should be addressed. Note that the proposed ISO standard was not approved April 1st. The balloting period was extended to July 1st due to irregularities in the process.

What is the status? A world-wide literature survey and report is in progress. From this will come recommendations for a scientific testing program designed to carry out the necessary testing to satisfy the concerns of the various interested bodies. Input will be sought from these bodies to help design the testing program. It is expected that the proposed program design will be completed within six months along with the completed literature survey and report.

Thank you again for your valuable communications. We trust that you will use our input to further advance the knowledge in the community you serve.

Notes

1. Mechanical pulp=Groundwood, thermomechanical pulp (TMP), refiner mechanical pulp (RMP).

2. The lignin level of the CTMP-containing fine papers is less than 15% of the lignin level found in newsprint!

3. The 6.5% lignin level in the last line of the table represented an extreme case produced for and tested by NISO in developing the revision to ANSI standard Z39.48 (Permanent Papers). Commercial grades are likely to contain less than 4% lignin, or 1/6 of that found in newsprint.