Volume 16, Number 5
Oct 1992

A Discussion on Deacidification and Pollutants

Several familiar technical issues were debated or discussed at the May 1991 IFLL/ICA conference on preservation research which were not mentioned in the September 1991 report in this Newsletter, because they were neither news nor part of a paper presented there. However, they deserve attention because they are debated and discussed in the field, and comments from scientists on matters of general interest are generally welcome. The issues are deacidification and pollutants, appropriateness of the fold test, and buffered paper for photo enclosures. The comments are transcribed from notes taken during the question periods following presentations, and subsequently confirmed with each speaker named. Some of the written comments they supplied have been interpolated below because they express what the speakers meant, if not their actual words.

Deacidification and pollutants: Françoise Flieder said they found that chemical pulp papers were more vulnerable to pollution after deacidification than they were if they were not deacidified. Their research is one aspect of the Step program, The Effects of Alr Pollutants on the Accelerated Ageing of Cellulose Containing Materials." Chandru Shahani's reply was that if the deacidified paper lasts longer, it is better even though it absorbs more pollutants. Frank Preusser, who had to leave early, left some written comments on this subject, and asked that they be read during discussion: "Concerning the effect of pollution on deacidified paper: There is at present no cause for panic. The French study was done with extra high pollutant concentrations. The advantage of deacidification can often outweigh the influence of air pollutants." Someone said that 20 or 30 years ago a study found that certain kinds of paper (made from certain pulps?) attracted sulfur dioxide preferentially; there may be other relevant research in the older literature. Judith Hofenk de Graaff, in her own comments, noted that "if acid paper is not deacidified it will deteriorate much faster than deacidified paper, [which happens to absorb air pollutants faster]."

The fold test: Françoise Flieder asked why the fold test had been chosen as a measure of strength in an aging test; it was a specious measure, she said. Chandru Shahani said that the Library of Congress lab had just finished a project comparing fold, tear, tensile, burst, zero span, viscosity, hot alkali solubility and a few other tests, on three sets of papers aged for 60 days. Almost every test had a big standard deviation if it was sensitive enough. Fold endurance is probably the most sensitive since it registers a 100% loss, while other strength properties show a 20 to 40% loss. However, fold endurance ceases to be of any significance at very low fold values. A fold of zero may still leave substantial strength by tear or tensile. After this point when fold endurance can show no further decrease on aging, tensile strength may decline by another 30%. The fault is not in the fold endurance test, but in paper; it is not a uniform material. If the wide spread of the readings is seen as bothersome, you can take 14 measurements, discard the two highest and two lowest and use the rest to compute an average value and standard' deviation.

Buffered paper for film storage: Judith Hofenk de Graaff asked James Reilly what his current opinion was on this topic. He said he and others at the Image Permanence Institute contributed to the recommendation that buffered (calcium carbonate-filled) paper not be used for storing photographs. When they were investigating albumen prints, they knew only part of the truth. Now their position is that it makes little difference. Their original concern was for the gelatin or albumen, which are proteinaceous--but that is usually not the problem. They currently recommend buffered paper envelopes for sheet film negatives.