[Nhcoll-l] Issues with low temperature treatment?

[Joachim Händel]

Hi Tonya,
we have been using this method for over 10 years with very good results.
A physicist told me that lower temperatures (-30 °C) are better than -20
°C, as smaller ice crystals form here.
Above all, it is more effective against collection pests.
We freeze the objects at -32 °C for at least a week.

The problem is not actually the freezing, but the thawing.
However, condensation forms during thawing, which could damage the
objects. It is therefore best to wrap the specimens as tightly
as possible in foil, trapping as little air as possible. This should
minimize the amount of moisture in the air that condenses
during thawing.
Condensation can attack the wires inside or soften the objects a little
or damage the ink on old labels.

It is not necessary to wrap insect-drawers separately in foil (in my
opinion!). I have carried out tests and found that the wooden
boxes buffer the fluctuations in humidity very well.

However, it is important to remove the objects carefully from the
freezer (especially delicate insects) and leave them to thaw in
peace, as the frozen structures are fragile and can be damaged by
vibrations.

Good luck
Joachim

 
--  
Joachim Haendel
 
Center of Natural History Collections
of the Martin Luther University (ZNS)
- Entomological Collection -

Domplatz 4
D-06099 Halle (Saale)
Germany

Phone:  +49 345 - 55 26 447
Email: joachim.haendel at zns.uni-halle.de

>>> "Haff, Tonya (NCMI, Crace)" <Tonya.Haff at csiro.au> 29.02.2024, 06:53
>>>


Hello all,

 

I am wondering if any of you can give me feedback how your specimens
have responded to low temperature treatment for pests.
Specifically, I’m interested in what types of specimens you’ve used low
temperature on (freezing), at what temperatures, and if
you’ve observed any negative effects on your specimens as a result of
colder temperatures? I’m especially interested if any of you
all use temperatures between -30 and -40C, and whether or not you’ve
noticed any effect on your specimens, relative to say -20C.
We are trying to optimise our pest treatment while mitigating risk to
our dry specimens, which include pinned insects, study
skins, and bones. We will be using refrigerated shipping containers to
do this work, which will be on large numbers of specimens
at a time.  I think we understand the parameters, but I would be very
interested to hear especially about direct experience,
caveats, things to watch out for, etc.

 

Thanks so much!

 

Tonya

 

-------------------------------------------------

Dr. Tonya M. Haff

Collection Manager

Australian National Wildlife Collection

CSIRO

+61(0)419569109

https://www.csiro.au/en/about/facilities-collections/collections/anwc
[https://www.csiro.au/en/about/facilities-collections/collections/anwc]

 
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