Last week a number of us here in the Special Collections and Preservation departments at Parks Library, in addition to other archivists and private collectors throughout the Midwest, attended a Care and ID of Photographs workshop presented by photograph conservator Gawain Weaver. The workshop was full of information on the history of photography and photographic processes, and identification techniques. The four-day workshop was hosted here at Parks Library, and a summary of the the workshop can be found at the library’s preservation blog.
Gawain Weaver discussing the dye layers of various chromogenic (color) photographic materials.
What we learned in the workshop can now be put to good use with our collections. In putting together this post, I tried to find a few examples of older photographs in our collections. Most of what we have are silver gelatin prints, but older photographic processes are also in the mix. For instance, many of the early images of campus are on glass negatives. Below is a dry plate negative of the Campanile, probably from 1912. The date is barely discernable on the negative, but with the scan one can zoom in to the date scratched at the bottom of the plate.
I scanned the negative first as a positive so the features of the glass negative could be seen more easily. The dry plates, which came after the wet-collodian negative process (for the basic steps of this process, visit the George Eastman House’s description), were a very important invention in the history of photography. For instance, unlike the wet-plate negatives, they could be bought ready to use from a manufacturer, were more sensitive to light and so needed less exposure time, and did not need to be processed immediately.
The same glass negative scanned as a negative, and seen as it might appear if a print was created from the negative.
The glass negatives were used to produce photographic prints. To the right is a silver gelatin print from develop-out paper (DOP), also from 1912. This photograph was developed by briefly placing the negative on the paper, and then completing the development process by using chemicals. Previously, many photographs were developed using printing-out paper (POP) by exposing the negative, placing the negative on the printing-out paper, and then exposing the negative and paper to light for a period of time.
The Washington Party image above, and the image to the right of a 1910 domestic economy cooking short course, both show evidence of something called silver-mirroring. Silver-mirroring is one of many good reasons that archival collections are stored in a temperature and humidity controlled environment. Environmental factors, such as heat and humidity, can cause a variety of damages to photographs. The Special Collections reading room should be one of the cooler areas in the library throughout the year, and the storage areas have even lower temperature and humidity levels.
Glass plate negatives, silver mirroring, identifying silver gelatin DOP prints, and caring for photographs were just one of many topics covered during the workshop. I can honestly say that it was one of the most enjoyable and informative professional development opportunities I have had, and it took place here at our own Parks Library!