[Nhcoll-l] Freezer recommendation

[Yatskievych, George A]

Hi Gali,

At the Tex/LL herbaria at the University of Texas, we use -80 C freezers (two 14 cubic ft chest freezers), but we run them at -60 C to lessen stress on them.  These freezers are emptied after at least one week and then refilled with room temperature specimens in boxes. We put all boxed materials to be frozen in plastic bags, mainly to minimize condensation as the materials warm after freezing. We have not found this protocol to adversely affect mounted or unmounted specimens. Our US Dept. of Agriculture requires as part of our import permits for specimens arriving from other countries that incoming materials spend at least two weeks at -20 C or one week in a -80 C freezer. We use the colder freezers to cut processing times in half, because of the volume of specimens that we need to freeze.

We abuse our freezers, because it stresses the compressors to have to cool down a full compartment of room temperature specimens to -60 C on a weekly basis. Labs that store DNA or other temperature-sensitive samples generally are adding small volumes of new material to an existing collection of samples. Thus, one should not mix samples intended for longterm storage with those being treated for insects to avoid sensitive samples being subjected to large temperature fluctuations on a regular basis. Additionally, we have to defrost our freezers every 2-3 months.

Balancing the time savings, it is worth noting that -80 freezers are as much as five times more expensive as -20 freezers of similar capacity. Depending on your hudget and space, this may be a practical factor.

Be well,

GY

George Yatskievych, PH.D.
Curator, Billie L. Turner Plant Resources Center
University of Texas at Austin, Main Bldg, Rm 127, 110 Inner Campus Dr, Stop F0404
Austin, TX 78712-1711
tel. 512-471-5904
e-mail george.yatskievych at austin.utexas.edu


On Aug 11, 2024, at 6:58 AM, Gali Beiner <gali.beiner at mail.huji.ac.il> wrote:



Dear All,

I'd like to ask for opinions regarding the choice of a freezer for our herbarium. The herbarium already has a -40C freezer for pest control purposes, but the combination of large quantities of incoming material for freezing with questions regarding additional possible uses for the freezer raised the question whether a new, additional freezer should be a -40C freezer or a -80C freezer.

Generally speaking, pest control does not usually require temperatures as low as -80C, but DNA preservation (samples, tissues from non-herbal collections) does. Would you consider keeping a -80C freezer to serve both purposes as need arises? I'm curious to hear whether other herbaria use -80C freezers or choose higher temperatures. There is of course the question of cost vs actual requirements, and the main requirement right now is for pest control prior to entry into the herbarium.

A penny for your thoughts,

Gali
--
[https://docs.google.com/a/mail.huji.ac.il/uc?id=0B5B3I3QnN7dsSzNkbGlLNDNGWG8&export=download]Gali Beiner (ACR)
Conservator, Palaeontology Lab
National Natural History Collections
The Hebrew University of Jerusalem
Berman Building, Edmond J. Safra campus, Givat Ram
Jerusalem 91904, Israel
Fax. 972-2-6585785
gali.beiner at mail.huji.ac.il<mailto:gali.beiner at mail.huji.ac.il>
https://nnhc.huji.ac.il/?lang=en
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