[Nhcoll-l] Freezing large specimens on formalin

[Hawks, Catharine]

Hi Esther

Unfortunately, formaldehyde polymerizes at low temperatures. This means that the equilibrium necessary for fixation is disrupted by low temperatures. The free formaldehyde in solution will polymerize, becoming large molecules that will not participate in fixation and this will drive the equilibrium equation in the wrong direction, slowly unfixing your specimens.  It is possible that once fully frozen, the reaction might be slowed, but it would unquestionably still do damage.

If specimens are prepared only by denaturation in alcohol (no formaldehyde fixation), low temperatures are a great way to foster preservation.

Cathy
Catharine Hawks, PA-AIC, FIIC
Museum Conservator
National Museum of Natural History
NHB 394 MRC 106
Smithsonian Institution
PO Box 37012
Washington, DC 20013-7012
Office 202.633.0835
Conservation 202.633.4041
Cell (work) 202.701.8458
Cell (pers) 703.200.4370



From: nhcoll-l-bounces at mailman.yale.edu [mailto:nhcoll-l-bounces at mailman.yale.edu] On Behalf Of Esther Dondorp
Sent: Tuesday, September 02, 2014 5:29 AM
To: nhcoll-l at mailman.yale.edu
Subject: [Nhcoll-l] Freezing large specimens on formalin

Dear Colleagues,


We have a large specimen tank (7*2*2 m) with specimens on formalin. For the construction of our new museum building, we have to get rid of these specimens temporarily until the new building with new specimen tanks is ready. Because storage in alcohol or formalin somewhere outside the museum will be a challenge, we were thinking of maybe storing these large specimens frozen in a cold storage. And when the new building is ready (somewhere in 2017), to thaw them and to change them gradually to alcohol.

I know freezing is not good for the specimens, but maybe it is different when they have been sitting in formalin for soo long?

I would really appreciate hearing your thoughts on this.

Best wishes,


Esther Dondorp

Collection manager Reptiles and Amphibians
Naturalis Biodiversity Center


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