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Subject: Deterioration of photographic negatives

Deterioration of photographic negatives

From: Christopher Gray <methistory>
Date: Friday, October 26, 2007
Juliette Baxter <jbaxter [at] northamptonshire__gov__uk> writes

>We have a large collection of cellulosic photographic negatives from
>a construction company (dates not known but likely to be 1930s
>onwards). Sections of the collection are showing signs of
>deterioration--distortion, bubbling of the emulsion, adhering to
>glassine sleeves. ...

Discussion continues on this list regarding cold storage of older
negatives. My 40,000 negatives run from 1936 to 1973, and are all
4x5 sheet film, shot by a single photographer.  However, from
destructive  testing (that is a fancy term for selecting some
marginal negatives, clipping  off corners from each, and burning
them to see which are nitrate) it was clear  that the photographer
mixed nitrate and acetate within the same years; there is  no clear
dividing line.

Mark McCormick-Goodheart generously provided me with a simple
storage solution (big freezer; all negatives sleeved in groups of
12; sleeves put in the usual boxes; boxes triple-bagged; warming
negatives in a picnic cooler to eliminate thermal shock.  But it
also became clear over time (as he  predicted) that the 3% (?) of
the negatives that were acetate (not nitrate) did not adapt well to
freezing and warming, and over time--perhaps after the first
cycle--the base and emulsion of many of the acetates separated, or
separated far more than they were already.

So, without resources to do a neg-by-neg examination and
sequestration, we have just accepted those as a "sacrificial layer".
We can always send out individual negs to have the emulsion
refloated and flattened, if necessary. In 15 years it has not been.

Christopher Gray


                                  ***
                  Conservation DistList Instance 21:29
                 Distributed: Sunday, November 4, 2007
                       Message Id: cdl-21-29-004
                                  ***
Received on Friday, 26 October, 2007

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