Deterioration of photographic negatives

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. This only seems to be happening in one section of
>the collection and the archivist who accessioned the collection is
>not sure whether they looked like this when they arrived or whether
>it has happened in the 6 or 7 years since they entered our building.
>Is this degree of degradation possible in 6 or 7 years (they are not
>stored in a photographic store but in the archival store) or is the
>cause likely to be a previous home?
>
>Also the sheer quantity will mean that we are not able to deal with
>the problem--are there any reliable imaging services in the UK that
>would be able to create surrogates before the problem gets any
>worse?

The negatives are likely to be on cellulose nitrate or cellulose
acetate film base.  These are both unstable at room temperature and
will gradually deteriorate.  Both show various signs of decay at
first and then can very rapidly deteriorate, showing some of the
gross signs you mention, over the course of a year or two.  Most of
the decay will have occurred in the previous home with the final
'tipping point' having been reached since the collection was
acquired.

The best method of preservation is to reduce the temperature, for
the whole collection, to slow the rate of decay.  A lot of
information on how to do this is available on

    <URL:http://www.wilhelm-research.com/>

(including the essential repackaging).  Due to the speed of decay
you should reduce the temperature now to buy yourself time.  You can
then deal with the question of surrogates once the situation has
been stabilised.

The gasses that are evolved during the decay processes will be
harmful to the archives in the rest of the store (and not great for
people either).

Regarding imaging services, yes there are.  How large is the
collection?

Nicholas Burnett
Museum Conservation Services Ltd.
Cambridge, UK
+44 1223 830373
Fax: +44 1223 830374


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                  Conservation DistList Instance 21:28
                 Distributed: Friday, October 26, 2007
                       Message Id: cdl-21-28-009
                                  ***