In general, cooler temperatures are preferred over warmer temperatures for the storage of most natural history collections (because at cooler temperatures the processes of deterioration and level of pest activity are reduced). However, there are some important caveats:<br>
<br>Keeping fluid collection storage a few degrees cooler than the lab in which the containers are sealed is a good idea, because the cooler storage temperatures will improve the seals on the containers by creating negative pressure inside the containers. However, keeping storage much colder than the lab where the specimens will be used is not such a good idea:<br>
*Temperatures below about 15C cause problems with fluid preservatives--alcohols tend to layer (particularly isopropyl), formaldehyde begins to precipitate out as paraformaldehyde (indicated by a whitish cloudiness in the fluid), dissolved lipids will congeal, some compressible gaskets will lose regain and therefore permit some evaporation, and so on.<br>
*On the other hand, at warmer temperatures, the processes of deterioration go faster (e.g., extraction of lipids and proteins in alcohol) and evaporation rates are higher. <br>*Based on the above considerations, the ideal range for fluid collection storage is around 18C, but certainly no lower than 15C.<br>
<br>Lowering the storage temperature below flash point of the preservatives is not a good idea:<br>*To begin with, this is a theoretical idea, not a practical one (we have no evidence that a sub-flash point temperature will really reduce fire danger in a museum storage situation of containers of fluid preserved specimens on shelving in a controlled storage area). <br>
*A container of fluid-preserved specimens sitting on a shelf in storage will not catch fire all by itself--an ignition sources is required. Assuming that the ignition source is a fire in the storage area, then the temperature in the room is not likely to remain below flash point when there is a fire anyway--fire generates heat, so spending a lot of money to cool the entire storage area below flash point is pointless.<br>
*As Doug stated, cooler temperatures are much, much more expensive to maintain, and depend on functioning, reliable HVAC equipment. Its not a wise use of resources.<br>*For fire safety, you are much better served by eliminating ignition sources in collection storage and installing a wet-pipe sprinkler system. To reduce ignition sources, do not permit electrical outlets in storage, use safety switches and non-sparking light fixtures, do not store other materials with the specimens, use metal shelving, etc.<br>
*Temperatures below flash point will cause the above listed problems with preservative solutions. When a container at around 15C is taken into a warmer lab and opened, the precipitated paraformaldehyde will leave the container as formaldehyde gas as the container warms up, which creates a serious health hazard for the human using the specimens. <br>
*As Simon mentioned, changing temperature changes relative humidity. By excessively cooling the air coming into storage, you may create a relative humidity problem where you did not have one before.<br><br>Finally, some caveats concerning an ideal temperature of 18C:<br>
*A realistic storage temperature for the collection depends on several factors because it must be a set point that is achievable without major expense, must be a temperature that can be maintained with only minor fluctuations, and may vary during the year. <br>
*Storage temperatures can be made more stable by such things as locating storage in interior rooms (with no outside walls or windows), and by selecting set points that are in keeping with the outside air temperature, building type, and HVAC system. *Transitioning slowly between a warmer summer set point and a cooler winter set point in a temperate environment will produce a better storage environment than spending vast resources trying to maintain some arbitrary set point that exceeds the ability of your building, HVAC, and local climate to maintain.<br>
<div class="gmail_quote"><br>--John<br><br>John E. Simmons<br>Museologica<br>128 E. Burnside Street<br>Bellefonte, Pennsylvania 16823-2010<br><a href="mailto:simmons.johne@gmail.com" target="_blank">simmons.johne@gmail.com</a><br>
303-681-5708<br><a href="http://www.museologica.com" target="_blank">www.museologica.com</a><br>and<br>Adjunct Curator of Collections<br>Earth and Mineral Science Museum & Art Gallery<br>Penn State University<br>University Park, Pennsylvania<br>
and<br>Lecturer in Art<br>Juniata College<br>Huntingdon, Pennsylvania<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div bgcolor="#ffffff"><div><font face="Arial"></font> </div>
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<div style="FONT:10pt arial">----- Original Message ----- </div>
<div style="FONT:10pt arial;BACKGROUND:#e4e4e4"><b>From:</b>
<a title="marce_irene@yahoo.com.ar" href="mailto:marce_irene@yahoo.com.ar" target="_blank">Marcela Cosarinsky</a> </div>
<div style="FONT:10pt arial"><b>To:</b> <a title="nhcoll-l@mailman.yale.edu" href="mailto:nhcoll-l@mailman.yale.edu" target="_blank">nhcoll-l@mailman.yale.edu</a> </div>
<div style="FONT:10pt arial"><b>Sent:</b> Thursday, March 14, 2013 4:12
PM</div>
<div style="FONT:10pt arial"><b>Subject:</b> [Nhcoll-l] optimal
temperature</div>
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<td style="FONT-FAMILY:arial;FONT-SIZE:10pt">Hi All,<br>What
temperature would you recommend for the best
conservation of biological collections kept in
liquids (alcohol, formalin), squeletons and
embalmed animals? <br><br>
<div>Many thanks, Marcela</div>
<div><br></div>
<div>Marcela Cosarinsky (Curator)</div>
<div>Sala de Colecciones - Departamento de
Biodiversidad y biología Experimental</div>
<div>Facultad de Cs. Exactas y Naturales</div>
<div>Universidad de Buenos Aires</div>
<div>Argentina</div>
<div>email:
<a href="mailto:marce_irene@yahoo.com.ar" target="_blank">marce_irene@yahoo.com.ar</a></div></td></tr></tbody></table></div></td></tr></tbody></table></div></td></tr></tbody></table></div>
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