Hi Amy,

We are (also) currently implementing a cold storage rehousal project for
the negatives and color photographic materials in our collections. In order
to curb the effects of the defrost cycle, you will want to seal anything
stored in the freezer in vapor-proof packaging. This is addressed in the
NPS conserve-o-gram 14/12 (2009). I'll send the document directly to your
email since it won't post to the listserv. In short, the vapor proof
packaging is a double bagging method that helps to maintain the materials'
RH by creating a micro-environment that will be less susceptible to the
freezer's fluctuation in RH during the defrost cycle.

To briefly quote the document, "testing shows that the RH in the freezers
may go from 65% to 85% over the course of an hour, but the RH inside the
packages will only change about 1% within the same time frame." This
technique was recommended to us by a photograph conservator who assessed
our collections and consulted with us for the grant we wrote to fund the
project.

Hope this helps!
-Krista

On Thu, Jun 8, 2017 at 8:53 AM, Amy Minger <[log in to unmask]> wrote:

> Please excuse cross postings.
>
>
>
> We recently purchased a commercial grade freezer to utilize as cold
> storage for nitrate negatives within our collections. Prior to placing any
> archival materials in the freezer I ran an environmental test using data
> loggers. The results of this test show that the freezer runs a defrost
> cycle every 6 hours. As you would expect, during a defrost cycle both the
> temperature and relative humidity increase significantly. The *max*
> temperature was recorded as 19.73 degrees Fahrenheit, and the *max* RH
> was recorded as 92.33%. *Average* running temperature of the freezer was
> recorded as 1.44 degrees Fahrenheit and *average* RH was 75.54%.
>
>
>
> My two major concerns are the high RH readings, and the amount flux (in
> both Temp and RH) in such a short period of time. I’m seeing over a 20
> degree flux in temperature within less than 24 hours.
>
>
>
> Information quoted below is from the CoOL website and seems to indicate
> that as long as such low temperatures are maintained, RH is less of a
> concern. Thoughts?
>
> *“Relatively inexpensive cold storage is available through the acquisition
> of a large commercial freezer. The freezer should defrost automatically (a
> cycle of three times a day is acceptable). Recent research indicates that
> precise control of relative humidity is, on balance, not of primary concern
> at such low temperatures (McCormick-Goodhart, 1993). Therefore, humidity
> controls within the freezer, if considered cost-prohibitive, can be
> omitted.”*
>
>
>
> Has anyone out there used a commercial grade freezer for nitrate negative
> storage before and if so how did you address these concerns? Thank you in
> advance for any and all input!
>
>
>
>
>
> *Amy Minger, Archival Assistant for Conservation *
>
> *Arkansas State Archives*
>
> an agency of the Department of Arkansas Heritage
>
> email: *[log in to unmask] <[log in to unmask]>*
> office: 501.682.6905 <(501)%20682-6905>
>
>
>
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-- 
Krista Barry
*Assistant Curator *
*Logan Museum of Anthropology*

*       ---*
Beloit College
700 College Street
Beloit, WI 53511
(608) 363-2932
www.beloit.edu/logan

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