03/24/2024
Train Station, Kyoto, 1950s, by Kiichi Asano. These progressive closeups of a resin-coated (RC) gelatin silver print show a form of silver deterioration known as redox blemishes or red spots (they often appear red in transmitted light). The yellow you see is the color of smaller silver particles formed from the breakdown via REDuction and OXidation of silver. They are most often seen on RC prints, but were first noticed on microfilm in the 1960s, which caused a commotion in the preservation world since microfilm was supposed to be a medium for long-term records preservation, and here it was deteriorating. In the case of microfilm it turned out to be peroxides from the lignin-containing paper microfilm boxes that were initiating this deterioration. Changes in processing and storage boxes eliminated the problem, but redox blemishes would reappear in the 1970s with the introduction of RC black-and-white paper, advertised as more archival and superior in every way to fiber-base paper, but in the end a complete archival disaster. Instead of peroxides from poor-quality boxes, the oxidizing culprit was now the free radicals created by the combination of water molecules, titanium dioxide (the pigment in the RC prints that puts the white in black-and-white), and light. Once this issue became known various efforts were made to make RC prints less susceptible to this problem. And it worked, kind of. In the end, RC prints were a convenience-- faster processing, less curl, but a major downgrade for print permanence.
