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.

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:

A 4x5 pack film negative showing the adhesive attachment stain along the right edge, and the negative number exposed onto the negative in the lower left corner. The image is blurred and possibly out of focus. Some of the original adhesive is still present along the left edge, but even where the adhesive is absent a brown image or stain remains in the film. This could have been caused by a chemical reaction between the adhesive and the silver image or by the pressure involved in applying the adhesive tape during manufacture (pressure exposes silver halide emulsions).

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.