Freezing glass plate negatives

Martha Little <mlittle<-a t->sonic< . >net> writes

>Does anyone have experience freezing glass plate negatives?  Would
>this be acceptable procedure for them?  If so, are there specific
>guidelines we should follow (such as how slowly to bring up the
>temperature afterwards, whether to seal each box in a plastic bag,
>etc.)?  ...

The Peterborough Museum and Archives (PMA) has had experience
freezing silver gelatin glass plate negatives with very successful
results.  However, our circumstances were very different and options
were limited as we were in an emergency situation responding to a
flood.

In the summer of 2004, tens of thousands of photographic materials
including thousands of glass plate negatives were submerged by flood
waters.  The submerged photographic collection materials were frozen
within 24 hours of becoming wet and remained in freezer storage
while treatments were developed.

At the time of freezing, the collection was in varying states of
processing with some boxes being covered and others not.  Due to
time restraints, boxes were placed in freezer storage as is.  We did
not wrap the boxes while they were frozen.

To dry the negatives and return them to room temperature, a
non-thermal freeze-drying process was employed by the ROSCO Group
Document Restoration (now First-On-Site).  On average, one box of
negatives (approximately 150) would be slowly dried over the course
of a week.

To freeze and then re-warm the glass plates you could use a Critical
Moisture Indicator Packaging

Method creating buffered micro-environments that protect the
negatives from RH fluctuations.  We use this method for our film
based negatives. The link below will take you to an article by Mark
H. McCormick-Goodhart of the Smithsonian Institution.

    <URL:http://www.wilhelm-research.com/subzero/CMI_Paper_2003_07_31.pdf>

There have been no other signs of deterioration to the glass plate
negatives that were frozen over the past 10 years.

Good luck,

Nicole Christie
Conservator
Peterborough Museum and Archives
300 Hunter Street East
PO Box 143
Peterborough
Ontario K9J 6Y5
705-742-7777 ext 2480


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                  Conservation DistList Instance 28:25
                 Distributed: Friday, November 21, 2014
                       Message Id: cdl-28-25-004
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