One particular example of the importance of chemical inertness in photographic enclosure materials came from the experience of the Still Pictures Branch of the National Archives and Records Administration. About 15 to 20 years ago, a number of 4 x 5 inch duplicate film positives were made at NARA from sane WI photographs. These were well processed and placed into envelopes marked "Permalife" and "pH 8.51". In the mid 1980's some of the films were discovered to have evident signs of silver oxidation (red faded spots and silver mirroring). The storage conditions were reasonably good, with temperature control and 35 to 507. RR. It seemed that the envelopes were responsible for this deterioration, and as a precaution, they were replaced. Subsequently, the preservation staff at NARA made samples available to the Image Permanence Institute at Rochester Institute of Technology for research into the Photographic Activity Test, an accelerated aging method to evaluate the chemical inertness of photo storage materials.
Samples of these envelopes performed very poorly on the PAT test, and in fact became one of the "benchmarks" of known harmful materials which were used to establish the criteria for the PAT test in ANSI Standard IT 9.2. What is instructive about this example is not that "Permalife" is bad for photographs (Permalife is a trademark that has been used for many paper compositions over the years, many of which pass the PAT test with flying colors), but rather that the sin4)le descriptor "acid-free" does not guarantee chemical inertness towards photographs. Although these particular envelopes were made acid-free by the addition of buffers, other substances present in the paper did react with silver images. The rationale for the PAT test is precisely to check for such interactions. Twenty years ago the test methods to evaluate photographic enclosures did not exist, but now they do, and both vendors and users can use scientific methods to obtain assurance of chemical inertness.
Timestamp: Sunday, 03-Mar-2013 21:37:04 PST
Retrieved: Friday, 24-May-2019 06:52:46 GMT