The Abbey Newsletter

Volume 18, Number 4-5
Aug-Sep 1994


Papers from the ARSAG Conference, May 1994

by Ellen McCrady

ARSAG is an acronym for Association pour la Recherche Scientifique sur les Arts Graphiques, which means "Association for Research in the Graphic Arts." It is allied with and operates from the CRCDG, the Center for Research on Conservation of Graphic Documents, which is headed by Françoise Flieder.

The first ARSAG International Conference was in 1991. This one, the second, was held May 16-20, 1994, at the Institut du Monde Arabe in Paris. Its title was "Environment and Conservation of the Written Record, Images and Sound," which reflects the new emphasis on preventive measures rather than treatment of individual items; it also signals coverage of digital records, as well as books and paper. It was unusual in having nine papers that addressed the issue of paper permanence in the light of recent developments in the paper industry (lignin-containing fine papers, recycled paper and chlorine-free pulp). Those nine papers and related discussion are summarized in "Paper Permanence Debate Lends Drama to Paris Conference," in the June issue of the Alkaline Paper Advocate.

There were 37 papers in all. The ones that were particularly important or interesting are described below. Some papers cannot be described here because there was trouble with the sound system, and I was sometimes unable to receive the simultaneous translation over my earphones.

Klaus Hendriks of the Canadian Conservation Institute gave an eloquent justification for paper permanence standards that specify composition (e.g., presence of lignin or calcium carbonate) as well as performance (e.g., strength measures, either alone or in combination with accelerated aging). The paper companies that are eager to sell their high-yield pulp and the paper made from it (which contains high levels of lignin) want to see standards based only on physical tests after accelerated aging. They want to keep any mention of chemical properties out of the standards, and to revise the recently approved NISO and ISO standards before the scheduled interval between revisions is over.

Hendriks made a point in his talk that may explain this preference: Chemical changes become apparent long before the changes in physical properties do. To give an example that people in preservation are familiar with: Acidic paper is strong when it is new, but over time the acid works on it, and after several decades it reaches a state of terminal weakness. Hendriks drew a graph showing a similar delay in the fall of folding endurance after a sharp decline in degree of polymerization (DP), which is a chemical characteristic.

To quantify brittleness when a more precise measure is needed than the corner fold test, he advocated TEA (tensile energy absorption) or the recently developed brittleness index, to be described in a forthcoming issue of the Journal of Polymer Degradation and Stability in an article by X. Zou et al.

He warned against relying too heavily on accelerated aging in a standard because a specification for accelerated aging may not mean the same thing to everyone, and people may get very different results even if they use the same temperature, relative humidity and aging period. By way of illustration, he pointed out that we have learned recently that paper may perform only a fraction as well after aging within a stack as when it hangs freely in the oven.

Chandru Shahani of the Library of Congress presented a paper on "Desorption of Residual Ethylene Oxide from Fumigated Library Materials." Since OSHA lowered the permissible exposure limit for ethylene oxide (EtO) to 1 ppm in 1984, most institutions have stopped using it, although it is one of the few measures that kills both insects and mold. Part of the problem is removing the EtO gas from the treated materials.

The Library of Congress team found that the different materials they tested all required 10 to 30 changes of air in the chamber before opening the door, to bring EtO concentration in the vicinity down to 1 ppm. Motion picture films were the worst, with the highest affinity and the lowest rate of desorption. Fifteen air changes brought it down only to about 100 ppm. Then wood and newsprint; book paper with alum-rosin sizing and low lignin; vinyl sound recordings; and leather. The authors recommend sampling the air in the chamber several hours after fumigation is completed.

The debate over plastic vs. metal cans for storing film was continued at this meeting, with some enlightenment from relevant research. Like many of the presenters, Michele Edge of Manchester Metropolitan University first described the research she had done ("Factors Influencing the Breakdown of Photographic Film: Implications for Archival Storage"), then gave recommendations for practice, emphasizing the kind of research that was still needed as a basis for such recommendations.

The choice is among metal cans, plastic cans, and vacuum sealed bags (the FICA system). All of them are problematical because they contain the gases evolved during the process of degradation, which can go on even when oxygen is sealed out. All of them must be opened in order to inspect the film; for the FICA bag, this can be expensive, because the bag cannot be reused. Metal cans can catalyse reactions in the film that result in release of acids. Nitrate film frequently corrodes the cans it is stored in, for this reason. Plastic cans have less buildup of acid inside, but they degrade in their own right, mostly by oxidation, producing peroxides and lowering the viscosity of the film (low viscosity is a result of degradation).

She may not have said this explicitly, but some people are recommending that containers be dispensed with altogether, and the vault kept at a low temperature and RH instead. Others are using cans with sensors built into the sides that change color visibly when acids build up above a certain level.

Régis Ramière (ARC-Nucléart, Grenoble) reported joint research (with CRCDG) on gamma radiation, a method of pest control that, like EtO, kills both insects and mold. Gamma radiation, properly performed on materials, is not a health hazard and does not make the materials radioactive or produce offgassing like EtO. It is used routinely in some Eastern Europe institutions. The problem is that it degrades the materials to a certain extent, and since it does not have a lasting effect, in practice it would have to be repeated on the same materials every time there was an infestation. It is possible to use a lower dose if radiation is used in combination with heat. The question, he said, is whether there is an effective but harmless dose.

They tested at various doses up to 3kGy, with and without preconditioning to 30°C and 95% RH, in air and in nitrogen, to prevent paper deterioration. The materials were than aged for a week at 80°C and 65% RH.

Francoise Flieder gave the results. They identified the mildest conditions that would get all 16 of the strains of fungi they tested. However, books warped and cockled when subjected to high humidity. All four kinds of paper tested retained their physical characteristics after treatment (tensile and burst), but copper number and degree of polymerization, the two chemical measures used, were worse. You can't ignore these chemical indexes, she said. They concluded that gamma radiation could not be recommended under any conditions. They do not know what to recommend instead. They are looking into beta radiation.

A paper by five Kodak authors was read for them by Guy Manas of Kodak-Pathé: "Molecular Sieves: An Aid to Film Preservation." This 1993 Kodak invention offers a way of controlling the "vinegar syndrome," or deacetylation of cellulose triacetate film. Molecular sieves are basically dessicants like silica gel, only more efficient, and they also absorb solvents and pollutant gases. The molecular sieve is a crystalline form of sodium alumino-silicate (zeolite), a porous solid which can be manufactured with small pores in any size, which absorb and trap any molecules that will fit inside the pores. For instance, acetic acid, sulfur dioxide, hydrogen peroxide and water are trapped by molecular sieves with pores of 4 angstroms.

Use of molecular sieves significantly slowed the decline in pH and reduced the level of moisture and contaminants of film aged in enclosures, in the research reported here. They can tell the molecular sieve is capturing acid vapors because they have developed a way of monitoring concentrations using 3M vapor monitors and gas chromatography. Testing continues, at Kodak and at beta sites around the world.

Jacques Lafon described a new fire suppressant gas that does not harm the environment like Halon does, and is not dangerous to people like 100% carbon dioxide is. Called Inergen, it consists of a mixture of nitrogen (53%), carbon dioxide (8%) and argon (40%). When discharged and mixed 50/50 with air, the proportion of oxygen is too small to support a fire, but is large enough to support life. The increased percentage of carbon dioxide stimulates respiration. The investment for installation is small. (But I did not hear him explain how sure one can be in practice that the air/Inergen mix will have the right proportion of oxygen.)

Brigitte Leclerc described the method used to monitor and control atmospheric biocontamination in the stacks of the Bibliothèque Nationale over a period of three years. It involves regulation of temperature and relative humidity, disinfection of the air and surfaces and site cleanliness. Monitoring stations were placed fairly close together, only four or five ranges apart.

[To be continued]

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