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Associations and InstitutionsAnnual 

64th IFLA Conference Logo

   64th IFLA General Conference
   August 16 - August 21, 1998


Code Number: 045-114-E
Division Number: VI.
Professional Group: Preservation and Conservation
Joint Meeting with: -
Meeting Number: 114.
Simultaneous Interpretation:   No

A papermaker's view of the standard for permanent paper, ISO 9706

Inga-Lisa Svensson
Mo & Domsjö AB, Örnsköldsvik, Sweden


Ylwa Alwarsdotter

Stora Fine Paper AB, Nymölla, Sweden


The increased demand of paper has always led to paper with lower permanence. With time it was understood that acidity was very important for the deterioration but there are also other reactions that contribute and made it impossible to predict ageing.

In 1993 the International Standard, ISO 9706, was approved but the dispute now is whether lignin is of harm or not. Our opinion is that as long it is not proved that that it is harmless we can not take the risk to continue to jeopardise our cultural heritage and allow material that for some reason lacks scientific certitude to be used as permanent paper.

It is important that all interested parties participate in the work through their national standardisation organisations.


Papermaking in the old days

Papers made during the middle ages are often very well kept, while most papers manufactured during the last hundred years have relatively low permanence. During those early days, paper was made from cotton and flax and it was sized with gelatine or other alkaline sizes. Due to washing during the treatment of the fibres it contained a few percent of calcium carbonate.

The amount of raw material for paper was limited and when Scheele discovered chlorine in 1774, dyed rag could be bleached and used for paper. The bleaching with chlorine caused, however, oxidation of the cellulose and slightly lower permanence.

The increased demand of paper needed more efficient manufacturing processes and in 1806 a new sizing procedure was developed. Rosin size was precipitated on the fibres with alum. Alum is acidic and a slow hydrolysis of the cellulose could take place in the paper. Alum also took away the calcium carbonate left from the washing procedure. This caused again decerased permanence of the paper.

New printing techniques increased the demand of paper even more and large efforts to find other raw materials were necessary. In 1858 the groundwood process was developed and later on in 1874 the sulphite cooking process. Now wood could be used and there were no limitations for paper production. These early procedures to defibrillate wood fibres by grinding and the acid sizing procedure caused the real low permanence.

What influences permanence?

During the first years of the twentieth century, acidity was discovered to have a great influence on paper permanence. Accelerated ageing became a test method to predict natural ageing and folding endurance was a sensitive evaluation method. In early works, accelerated ageing in a dry climate that gave good correlation with natural ageing particularly on papers made from cotton. Addition of calcium carbonate to the paper was shown to increase permanence. The dispute was, however, whether the deterioration was due to the fibres, cotton or wood, or to the acidic pH.

It is likely that the hydrolytic deteriorating processes dominate for papers made from pure cellulose, e.g. cotton, thus giving this good correlation between accelerated and natural ageing. Modern papers contain, however, also other substances, lignin and hemicelluloses from wood and papermaking additives, this causes different climate, temperatures and relative humidities, to give different results. It might be that oxidative and crosslinking reactions play a greater roll and thus make it more difficult to predict ageing. Natural ageing is also dependent of the conditions under which it takes place. There is no standard climate for natural ageing.

For many years cotton linters and addition of small amounts of calcium carbonate was used to make papers with good permanence. This was the situation in the 1980s when the International Standardisation organisation through its Technical Committee for Information and Documentation/ Physical keeping of Documents; ISO/TC46/SC10 started its work on a standard for permanent paper.

The first standard

In Sweden the shadow working group had experts from archives and libraries and from the paper industry. We discussed the needs and the possibilities and we studied the paper process and the situation at the archives and all parties got an understanding of each other's problems and difficulties. As papermakers we understood that our cultural heritage was disappearing due to wrong papermaking procedure and by that time we had better procedures, neutral systems with calcium carbonate as filler, and we were able to switch over. ISO 9706 Information and documentation - Paper for documents Requirements for permanence was registered as a work item. Eight countries took part in the working group and thirteen countries approved the Committee Draft and one (Australia) was against.

What is the impact of lignin?

Now the International Standard ISO 9706 has been in force for four years. The pH issue is not a problem, that means that there is an agreement that the hydrolytic reactions are the most important ones for the deterioration of paper, the dispute is whether lignin is of any harm or not. Oxidation and crosslinking reactions are there and we do not know their importance for deterioration and permanence. Some scientists even claim that lignin might even be a benefit to permanence.

As we see it, the proof is the largest problem. During the drafting of the standard several methods for accelerated ageing was studied. A temperature of 80oC and a relative humidity of 65 % up to 24 days was used in an interlaboratory test. Some acid and lignin containing papers gave very good strength after accelerated ageing, even better than neutral papers made of chemical pulps and that we knew for sure is not the case in natural ageing. The decision became to exclude accelerated ageing from the requirements. An Informative Annex in the standard explains why. There were three reasons

Accelerated ageing is still used for studies of permanence and is often claimed to prove that papers containing lignin show very little deterioration. And that is right, they show little deterioration in accelerated ageing if the conditions, temperature and humidity, are the right ones. But, as they did in the beginning of this century, we have to correlate with natural ageing and that takes time. Another possibility is to know what reactions take place and how harmful they are.

During the time when the working group was in action, experts from archives and libraries and papermaking came to solutions that were reached due to understanding of each other's problems. We based our decisions on mutual respect and as papermakers we found that the fear for lignin containing papers was so strong among the experts from archives and libraries. They had the experience of too many deteriorated papers that had to be restored at high costs. We had also to take our responsibility for the cultural heritage. Now that we had the know-how to produce paper with high permanence there were all reasons to take every precaution and exclude material that we knew too little about.

However, ISO 9706 does not state any limit for lignin content. Instead, the standard has a limit in Kappa number, a figure that expresses the material's sensitivity to oxidation. The logic was; if the paper is sensitive to oxidation, it is likely to get oxidised with time and thus unstable over long time periods.

There are also other papers that contain easily oxidised substances, for instance some coated papers. Soft latex binders with a high amount of double bonds is also easily oxidised and give high Kappa number depending on the composition of the coating layer and the amount of coating on the paper. Some of these papers do not fulfil the requirements of ISO 9706 either, though they may have a high degree of permanence they are not suitable for library and archival purposes.

Why keep the existing International Standard?

We think that the standard accepted in 1993 should stay as it is until new results have proved that other criteria can describe the requirements for permanence. The International Standard is based on the present state of knowledge and as long as nothing new has been proved we cannot recommend a revision of ISO 9706. We are convinced that if new knowledge comes out which proves lignin to be harmless it will be possible to revise ISO 9706 in due time. There is also an American National Standard ANSI/NISO Z39-48-1992, American National Standard for Permanence of Paper for Publications and Documents in Libraries and Archives. The limiting values of two of the required characteristics viz. tear resistance and resistance to oxidation, differ slightly from those of ISO 9706. TheANSI/NISO standard was reaffirmed in 1997 for five years. The NISO members were asked to reaffirm the standard with the understanding that when the research on the lignin issue is completed and more information is available they will review the standard and consider if revising the standard is appropriate (Information from NISO).

In the meantime different parameters influencing ageing must be studied. An ISO standard ISO/CD 15659 Information and documentation - Archival board - Migration test is under development by ISO/TC46/SC10/WG1. It is intended for testing of boards to be used to protect archival material. It has been found that some papers of too low quality might discolour adjacent papers. We have made tests with this method and found that some papers containing about 20 percent of CTMP causes a considerable discoloration of the blotting paper close to it, while others do not. What is the difference between these materials? In this test only the change in brightness is measured. Some experts claim that this discoloration might also decrease strength

ASTM, American Society of Testing and Materials and its Institute for Standards Research, is engaged in a multi-year research programme to create scientifically sound methods for the prediction of the life expectancy of printing and writing papers. The goal is expanding understanding of the fundamental mechanisms of paper ageing and developing accelerated ageing test methods that correlate well with natural ageing results. To ensure maximum reproducibility, papers were specially made. They cover a range of different compositions. This is interesting. This will give us indications what papers deteriorate less than others will. But will it also give better knowledge of the reactions taking place in ageing papers? As we said before what do we mean with natural ageing?

Your contribution to standard modifications

The future of ISO 9706 Requirements for permanence for paper will be very interesting and we hope that this will encourage many of you to take part in the process of revising the standard. That can be done by joining ISO/TC46 through your national standardisation organisation as a P- member or by A-liaison members such as IFLA.