[NHCOLL-L:2507] Re: freezing mounted specimens

[kwellspring]

Greetings Kathryn,

Our museum is also in the process of moving, and I had to confront some of
these same issues last summer when I packed up the taxidermy collection and
some of our large osteological specimens.  We wanted to deal with our pest
problems on site, as we were moving them from a non-pest
resistant/temp-humidity controlled environment, to a "clean" facility with
temp-Rh controls.  I, too, was trepidatious about the effects indiscriminate
freezing, so I availed myself to some printed resources (Moving the
Mountain: A Guide To Moving Collections, published by the Science Museum of
Minnesota) and more knowledgeable colleagues (taxidermists at the
Smithsonian Institution).  The advice I followed was to freeze our entire
taxidermy collection (including bird and small reptile/mammal mounts, as
well the trophy heads) and most of the large osteo collection; the lone
exception was the elephant skulls, as it was determined the ivory was likely
to crack should the temperature drop/rise too quickly.

My most pressing concern at this point was not the effects of freezing, but
the potential effects of condensation on the specimens; many of our bird
mounts were stored inside plastic bags, and were to be moved and stored
inside large polyethylene boxes.  As I was packing these birds during a
particularly humid August, I was wary of condensate becoming trapped inside
of the bags/boxes and later causing mold growth on the specimens.  We
attempted to find mobile freezer trucks with a de-humidification feature,
but were unable to locate any in our area.   After some discussions with a
SI colleague, I was (partially) reassured that this was not likely to occur.
I was also concerned that the plastic boxes (household, not commercial
grade) the birds were stored in would crack when frozen.  I spoke at length
with the box manufacturers and was told this would not occur.  Still
skeptical, I elected to run an onsite experiment: the manager of the college
kitchen facility was kind enough to allow me put several of our plastic
storage boxes through a freeze cycle (four day freeze, five day defrost,
four day freeze) in the food storage walk-in freezer.  I was most relieved
when I finally dug them out--intact--from behind the innumerable cases of
frozen pizza.

Sufficiently confident, we rented a freezer truck large enough to
accommodate all of our crated/boxed up specimens in one go.  The freeze
cycle went relatively smoothly  (in spite of one of the generators failing
briefly‹be sure to have a back-up if you use generators!), and the
collections were moved into the new facility.  I have been checking on them
every three weeks (they are currently stored off-site) and have so far found
no cracked teeth, shells, bills or glass eyes, or signs of fungal blooms.  I
do not know of any definitive way to check the integrity of plaster of paris
that may be inside of the trophy heads, but I can report that they appear
unaltered from their pre-freeze state, and I have not noticed any flaking
material falling away from them at the seams.

It appears that in the case of your museum, more serious
specimen-by-specimen consideration may be necessary, as you indicated that
some of your mounts possess the dubious distinction of being both "old" and
"valuable".  In the interests of full disclosure, I should indicate that
many of our mounts were of venerable age and questionable scientific
valuable (in the sense that they represent locally common or unidentified
organisms with no collection data; or that they were in such poor shape to
begin with that any damage they sustained by freezing was not likely to
substantially worsen their condition).  I would certainly suggest that you
directly contact your colleagues at institutions that are likely to have
moved and/or de-bugged their "skin & bone" collections in the recent past.
They may be in the best position to answer your most specific questions.

I hope some of this information may be helpful to you.  Please do contact me
off-list if I can provide you with any further details.  Best of luck in
this endeavor!

Kate Wellspring

______________________________
Kate Wellspring
Collections Manager
Pratt Museum of Natural History
Amherst College
Amherst MA 01002
(413) 542-2165
www.amherst.edu/~pratt





On 1/3/05 7:46 PM, "Kathryn Medlock" <kathryn.medlock at tmag.tas.gov.au>
wrote:

> We are currently in the process of moving our entire zoology
> collections to new and better storage and of course wish to ensure
> that pest problems are not just transferred. I might say that we have
> few problems at present and have treated things as the need arises -
> usually be freezing.
> 
> My problem now how to ensure the best way to de bug items prior to
> the move. The collection contains a lot of recent material but also
> includes valuable 19th century mounts of birds (cased and uncased),
> mammals, trophy heads as well as osteological material across a range
> of species. I have been attempting to find out what the best way to
> go will be.
> 
> I am very suspicious of just freezing everything given that it seems
> to be agreed in conservation circles that leather shouldn't be
> frozen. As you would be aware, mounts are made of a wide variety of
> materials - stuffing (straw, wood wool, fibreglass), wire or rode
> metal supports, possibly plaster of paris, glass eyes, wooden base
> that may contain dried vegetation etc etc. What happens to the bills
> of large birds, ivory, teeth, webbed feet etc? Surely these materials
> all react in different ways to the freezing process.
> 
> I have been told by some that freezing in OK, by others that teeth
> cannot be frozen. Bromide apparently fades feathers. Carbon dioxide
> is too dangerous and we are not set up for nitrogen.
> 
> Does anyone have any suggestions as to the best way to go. I am in
> favour of treating only if suspicious rather than a blanket treatment
> that may result in damage to the material.
> 
> Sincerely,
> 
> Kathryn Medlock
> Curator
> Vertebrate Zoology, Tasmanian Museum and Art Gallery
> 

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