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Subject: Cold storage for glass plate negatives

Cold storage for glass plate negatives

From: Gary Saretzky <saretzky>
Date: Wednesday, April 3, 2002
William L. Hopkins <whopkins [at] uwyo__edu> writes

>We are currently considering our options regarding placing our glass
>plate negatives into cold storage.  Our unit is set at 32 degrees F.
>with a relative humidity of 40%.  We are planning to place those
>plates that are in the worst condition into storage first, using a
>24 hour cool down period in a beverage cooler to slowly equalize
>conditions.  My question is will the cold conditions exacerbate any
>peeling of the emulsion from the glass plate or otherwise weaken the
>adhesion between the glass and the emulsion? ...

About twenty years ago, Dr. Klaus Hendriks and colleagues tested
freeze drying of a variety of photographic materials that had been
soaked in tap water and found that collodion glass plate negatives
were destroyed by this process. The image layer shattered in many
pieces. In the classic article, "Disaster Preparedness and Recovery:
Photographic Materials," by Hendriks and Brian Lesser (American
Archivist, 46:1, Winter 1983), the authors state, "One has to
conclude from these observations that negative glass plates made by
the wet collodion process--and collodion positives known as
ambrotypes and tintypes, which were made by a similar
process--should be kept in any collection in a way that will prevent
them from ever being flooded or soaked in water."

Hendriks and Lesser didn't state that freezing per se was bad for
collodion glass plate negatives, just soaking them first and then
freeze drying them. However, his research does suggest that your
concern is justified if you have collodion glass plate negatives and
are thinking about freezing them. Perhaps cool storage would be a
safer alternative.

You didn't state whether your glass plates were collodion or
gelatin.  In his tests, Hendriks found that gelatin glass plates
were much more resistant to damage caused by water and freezing.

A final comment--even if you find that freezing is safe, given that
freezers and refrigeration systems sometimes have mechanical
problems, it would be advisable to package all materials placed in
them to prevent moisture damage.  Packaging materials for such
purposes are sold by Metal Edge.

Gary Saretzky
Monmouth County (NJ) Archives

                  Conservation DistList Instance 15:68
                   Distributed: Friday, April 5, 2002
                       Message Id: cdl-15-68-001
Received on Wednesday, 3 April, 2002

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