Volume 8, Number 5
Oct 1984

Does Alkaline Buffering Affect Photos? Hard to Tell

In the June issue of this Newsletter, the advice of several photographic conservators was summarized, concerning the use of alkaline buffered storage materials with prints and especially with albumen prints. The consensus seemed to be that buffered materials should be avoided unless low humidity can be guaranteed and direct contact prevented. Recently, however, an attempt has been made to produce the bad effects that had been observed occasionally, and on which this advice was partly based; and the attempt was not successful. It was a project conducted by James Reilly under a National Museum Act grant, entitled "Evaluation of Storage Enclosure Materials for Photographs Using the ANSI Photographic Activity rest." The final report is dated March 1984.

There were two reasons why this study failed to incriminate buffered board and paper: 1) the effects, if any, were too small, and 2) the test used was not sensitive enough. In his words, from p. 27-28 of the final report:

The ANSI Photographic Activity Test is an empirical procedure which does not provide any information on the causes or mechanisms of harmful chemical interactions between enclosures and photographs. The purpose of this study was to obtain empirical results on a large number of enclosure products, not investigate root causes of deterioration; however, the influence of one ingredient in papers and boards was investigated: calcium carbonate buffering.

The question of the effects of buffered papers and boards was of interest because of earlier work done in this laboratory.^* When albumen print samples were made very alkaline by soaking them in solutions of borate buffer at pH 9.1 or in .1N NaOH, yellowing and fading were observed upon incubation at elevated temperature and humidity. From this work and also from trials of the Photographic Activity Test with a buffered paper in which small amounts of yellowing were observed, a tentative recommendation against the use of buffered enclosures with albumen prints was made.

However, the effects of the calcium carbonate buffer itself were not evaluated in this earlier work, and in the Photographic Activity Test with the buffered paper there may have been other causes not related to the buffering. For these reasons an experiment was designed which would directly measure the effects of buffering on albumen prints without interference from other paper components.

The experiment involved starting with Whatman #1 filter paper, macerating it in a blender, and forming hand- sheets with and without added carbonate buffering. The making of the hand-sheets and the determination of their ash content and alkaline reserve (according to the method of ANSI PH 1.53-1978) are described in detail in the Third Quarterly Narrative Report for National Museum Act Grant #FC-206537. Twenty-one buffered sheets were made which had an average alkaline reserve of 3.41%. Eighteen non-buffered sheets were also prepared.

Buffered and non-buffered hand-sheets were then incubated with albumen print samples in the manner described in the main body of this report for the other enclosure products [82 "archival quality" enclosure materials and 19 "non-archival" materials]. In two trials of the experiment, no significant differences were observed between the samples incubated with buffered and non-buffered paper, either in visual evaluations or in density change measurements. It is possible there may be small effects from the buffering over a longer term of incubation, but they were too small to be detected in this incubation procedure. More work should be done, but it seems clear that calcium carbonate buffering is not by itself a major threat to albumen prints.

* J. Reilly, "Role of the Maillard, or 'Protein-Sugar' Reaction in Highlight Yellowing of Albumen Prints." Preprints of the 10th Annual Meeting of The American Institute for Conservation, Milwaukee, 1982, pp. 160-168.