Tuesday, January 7, 2014
Monday, March 25, 2013
Treatment of Deteriorated Cellulose Acetate Negatives
VINEGAR SYNDROME. Before and After Treatment of a 4”x5”
cellulose acetatenegative by stripping the image pellicle from the deteriorated
acetate support.
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When photographic film with a cellulose acetate support
begins to deteriorate we say it has vinegar syndrome because it forms acetic
acid (among other deterioration byproducts) and smells like vinegar. The
acetate support also shrinks and becomes brittle eventually pulling away from
the gelatin image layer in patterns often called channeling. The plasticizer in
the acetate support comes to the surface and forms small bubbles between the
acetate support and the gelatin image layer. With all this deterioration and
deformation it becomes impossible to print or scan the negative and get a good
quality result. Cold storage is the only way to slow down this deterioration
process, but it can’t reverse deterioration that has already occurred. So for
some negatives it is necessary to separate the very thin gelatin image layer
from the deteriorating support. This technique of “emulsion stripping” was
first pioneered in Canada in the 1960s as a photomechanical layout technique
for combining graphic elements in the creation of camera ready art for
printing. It was adopted in the United States also for graphic arts purposes in
the 1970s and by the 1980s was being used for the first time as a conservation
method for deteriorated acetate negatives. It turns out that even after all the
dramatic deterioration of the acetate film base, the gelatin image layer is
usually still OK, and can be separated, scanned, and then stored safely. The
new digital image file can then be written back to a new sheet of
polyester-base film or stored in a digital repository. Gawain Weaver Art
Conservation has been performing this process for several years. Please contact
us to discuss your project.
Friday, September 14, 2012
Chromogenic Print Fading at Seal Rocks
This 8"x10" resin-coated chromogenic print from the early 1970s hung in the owner's living room for several decades. Light exposure was limited to the area of the print within the window mat opening. When the mat was lifted, the difference between thermal fading and light fading over the last 40 years was revealed.
Monday, October 31, 2011
The ghostly effects of platinum images
I recently found this platinum print, nearly panoramic by virtue of being two separate prints attached at the center. It's a platinum print of the sepia variety and what made it interesting to me was the dramatic image transfer effects that occurred as a result of being stored folded. Each half of the image has "transferred" itself on to the other half. For example, the two women standing in the flower garden on the right side also appear as ghosts in the road on the left side. Both of the buildings have also transferred their mirror images to the opposing side. The best explanation for this image transfer effect has been posited by Mike Ware. His theory goes something like this: the platinum image metal plays a key role in the conversion of sulfur dioxide (an air pollutant) into sulfuric acid, which causes the brown discoloration of the paper. We often see this effect on paper folders and protective tissues in contact with platinum prints and also on paper materials in contact with matte collodion prints (which are toned with platinum).
Wednesday, August 3, 2011
Kodak Notch Codes in the 1970s
Although I'm planning a much larger article on notch codes and the decoding of other information on (mostly Kodak) films and prints, here are a few notch codes for (mostly) 1970s color material that might be useful to some. All images are from different editions of the Kodak Color Dataguide:
Kodak Color Dataguide |
Kodak Color Dataguide 1966 |
Kodak Color Dataguide 1971 |
Kodak Color Dataguide 1974 |
Kodak Color Dataguide 1975 |
Kodak Color Dataguide 1976 |
Kodak Color Dataguide 1977 supplement |
Kodak Color Dataguide 1978 |
Wednesday, December 8, 2010
Kodak Super-XX Film Pack
Following a discussion about pack film on the Photohistory listserv I acquired an unopened Kodak Film Pack. The "Develop By" date on the package is March 1955. I will annotate and add further information, including pictures of developed film negatives at some point. But here are the pictures for a start:
Film Pack Diagram from C.B. Neblette, Photography: Its Principles and Practice, 3rd Edition (1938) |
Sunday, September 5, 2010
Boy Scout Jamboree: Dufaytissue from Dufaycolor
I recently acquired a few Dufaycolor transparencies and with them came a single print of a type I had never seen before. After a little research, the print appears to be a Dufaytissue (Dufay Tissue?), a modified version of the tricolor carbon process using carbon tissues on acetate supports for the individual color layers which are then assembled on a paper support. Although my example may not be typical, the Dufaytissue lacks detail in the highlights and shadows as well as sharpness compared to the original Dufaycolor transparency. This Dufaytissue image degradation is likely common given the difficulties inherent in making a continuous tone print from an additive screen plate with its color mosaic. Both images measure 6x9 cm.
Dufaycolor |
Dufaytissue |
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