[Nhcoll-l] optimal temperature

[John E Simmons]

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:

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:
*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.
*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.
*Based on the above considerations, the ideal range for fluid collection
storage is around 18C, but certainly no lower than 15C.

Lowering the storage temperature below flash point of the preservatives is
not a good idea:
*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).
*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.
*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.
*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.
*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.
*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.

Finally, some caveats concerning an ideal temperature of 18C:
*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.
*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.

--John

John E. Simmons
Museologica
128 E. Burnside Street
Bellefonte, Pennsylvania 16823-2010
simmons.johne at gmail.com
303-681-5708
www.museologica.com
and
Adjunct Curator of Collections
Earth and Mineral Science Museum & Art Gallery
Penn State University
University Park, Pennsylvania
and
Lecturer in Art
Juniata College
Huntingdon, Pennsylvania

>
>
> ----- Original Message -----
> *From:* Marcela Cosarinsky <marce_irene at yahoo.com.ar>
> *To:* nhcoll-l at mailman.yale.edu
> *Sent:* Thursday, March 14, 2013 4:12 PM
> *Subject:* [Nhcoll-l] optimal temperature
>
>               Hi All,
> What temperature would you recommend for the best conservation of
> biological collections kept in liquids (alcohol, formalin), squeletons and
> embalmed animals?
>
> Many thanks, Marcela
>
> Marcela Cosarinsky (Curator)
> Sala de Colecciones - Departamento de Biodiversidad y biología Experimental
> Facultad de Cs. Exactas y Naturales
> Universidad de Buenos Aires
> Argentina
> email: marce_irene at yahoo.com.ar
>
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