44th Annual Meeting, Photographic Materials, Tuesday, May 17, Separation Anxiety: Kiss Your Acetate Goodbye! – by Nicole Christie and Cindy Colford.

In a presentation related to the Disaster theme of the conference, speakers Colford and Christie spoke of the recovery of flood damaged photographic collections of the Peterboro Municipal Archives, in Ontario in 2004. The area wide disaster created such demands on affected infrastructure that the response began two weeks after the peak flood, which led to a decision to freeze all the of works, including glass plates and film negatives as other methods of drying had not been possible. The PMA participated in a CCI risk assessment which reported back with recommendations to keep all film stabilized in freezers for continued cold storage, and to identify cellulose acetate negatives as a specific priority for treatment due to their autocatalytic behavior, leading to eventual change and loss of values.
The authors, looking to Pavelka & Naipavel-Heidushke’s paper on successful treatment and separation of gelatin image layer from acetate support, called out Pavelka’s suggestion that insurance companies might provide financial assistance for treatment in their coverage. Following the protocol suggested in the article, the authors proceeded and achieved inconsistent results. They noted the process per negative could take up to ninety minutes, resulting in only four negatives treated over two days, They cited concerns of prolonged exposure of the negative to solvents, yet found it hard to keep solvent from evaporating, which could induce curl and tensions while drying. A new question developed, what was the difference between the article’s case studies vs. theirs? An obvious variable was the fact that these items had been frozen. Whether or not this actually factored into the negatives’ behavior. Consulting further with Greg Hill (currently of the Canadian Conservation Institute) & Gayle McIntyre (Sir Sandford Fleming College), the protocol was revised to include the following steps, which helped increase the reliability of the method across different negatives:

Silver gelatin pellicle being separated from acetate support
Silver gelatin pellicle being separated from acetate support

1. Remove material by cutting away some of the lip/edge of the negative to allow ingress of solvent
2. Prewet the negative using sequential solvents
3. Use visual and tactile clues to determine the moment of separation (need slide 3.1, 3.2.) not a fixed amount of time
4. If the gelatin is still disrupted, reshape while it is still wetted using gentle prodding (with  brushes on silicon release Mylar*) to lay flat before drying completely.  The unsupported pellicle, thin as tissue, can be left to release final residues of solvent in a non-stick drying pack in fume hood to offgas.
(More images of these steps available in the downloadable Kiss Your Acetate Goodbye images of layer separation, pdf file kindly provided by the speakers.)
The images, now supported on Mylar sheets, were digitized, and the storage solution after treatment includes use of polypropylene sleeves in a clamshell binder. In an added benefit, the items are no longer taking up space in cold storage. The authors report that after eight years, the images appear unchanged in these conditions. While having a positive outcome, the speakers note that is still a lengthy process involving time and material costs, requiring trained professionals. This technique may not be a catchall for all collections, but for prioritized ones, it can be effective management tool for severely decaying negatives.
*Additional note: Silicon tip tools may also be useful here. See related content from 2016 BPG Tips Session on Silicon Shapers, as found in art supply stores today among the brush selections for working thick paints, in the BPG wiki.