[Nhcoll-l] Freezer recommendation

[John E Simmons]

Gail,
I do not think using a -80C freezer for pest control is a good idea for
several reasons:
1. -80 is far colder than is needed to kill pests.
2. That temperature (-80) would subject the herbarium sheets, plant
specimens, adhesives, and etc. to a much colder temperature than ordinary
pest treatments which would likely result in damage. For example, it would
further dehydrate plant specimens unless they were very well sealed in a
controlled RH environment; the adhesives used to affix labels or specimens
to the sheets might fail at that temperature, and it would subject the
specimens to stress from dimensional changes that occur with extreme
heating and cooling cycles
3. Many people assume that freezing is innocuous, but like any treatment or
handling method, freezing affects the specimens, causing wear-and-tear
damage that accumulates over time.
4. Presumably the -80 freezer would hold both tissue samples (which do need
to be at -80) and any herbarium sheets being treated, but each time the
freezer is opened, and when warm materials are inserted into the freezer,
it disrupts the storage environment (by warming it and then cooling it down
again), which over the long term would likely shorten the useful life of
the tissues subjected to needless warming and cooling cycles.

Freezers have a relatively short life, particularly ultracold freezers, and
depend on a regular electricity supply. Given the uncertainties of climate
change, I encourage the herbarium staff to consider instead buying a -30
freezer for pest control and a liquid nitrogen storage system for the
tissues. Liquid nitrogen has the major advantages of few moving parts and
the ability to withstand long power outages.

Hope this is helpful,
John

John E. Simmons
Writer and Museum Consultant
Museologica
*and*
Investigador Asociado, Departamento de Ornitologia
Museo de Historia Natural, Universidad Nacional Mayor de San Marcos, Lima


On Sun, Aug 11, 2024 at 7:58 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
> --
> 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 <gali.beiner at mail.huji.ac.il>*
>
> *https://nnhc.huji.ac.il/?lang=en <https://nnhc.huji.ac.il/?lang=en>*
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