[Nhcoll-l] Humidity in collection rooms

[Dirk Neumann]

seconding Paul ... could also be cold outer walls, e.g., in subsurface 
buildings ...

And rust (metal corrosion) could also affect dry collections (e.g. 
rusting/corrosion of historic insect pins)

All the best
Dirk


Am 25.06.2021 um 16:32 schrieb Callomon,Paul:
>
> In our experience a recurring problem in wet collection environments 
> is the combination of ambient high humidity and lower-than-ambient 
> temperature. The dew point – the temperature at which water vapor 
> condenses – is a function of both factors; with ambient humidity but 
> below-ambient temperatures, such as in a room that has air cooling but 
> no humidity control, condensation happens when it would not if the 
> temperature was also ambient.
>
> Water will condense onto the coldest surface first, which tends to be 
> the glass bottle surface. Room dehumidifiers exploit this effect by 
> cooling a coil with refrigerant gas to present an even colder surface 
> on which condensation will thus happen first. Purpose-built fluid 
> storage rooms often have an air drier that removes vapor from the 
> incoming air before it is cooled, thus providing both humidity and 
> temperature control.
>
> Many years ago we constructed an entire building thus equipped, but 
> the cost of running and maintaining the driers got them switched off, 
> with disastrous consequences that have taken decades to remediate. The 
> entire building quickly became a mold farm and rust was rampant even 
> in recently-installed racking. Because the building had been designed 
> as a sealed system, there were no windows to open to at least mitigate 
> the worst effects.
>
> If you have high ambient humidity that cannot be lowered, therefore, 
> it might be safest not to cool the room much. This is suboptimal in 
> conservation terms, but the consequences of lowering the dew point are 
> rust, mold and other undesirable results of liquid condensation 
> running down your jars and over your racks.
>
> Paul Callomon
>
> Collection Manager, Malacology and General Invertebrates//
>
> ------------------------------------------------------------------------
>
> *Academy of Natural Sciences of Drexel University***
>
> 1900 Benjamin Franklin Parkway, Philadelphia PA 19103-1195, USA
> /prc44 at drexel.edu <mailto:prc44 at drexel.edu> Tel 215-405-5096 - Fax 
> 215-299-1170/
>

-- 


Dirk Neumann

Tel: 089 / 8107-111
Fax: 089 / 8107-300
neumann(a)snsb.de

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81247 München

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---------

Dirk Neumann

Tel: +49-89-8107-111
Fax: +49-89-8107-300
neumann(a)snsb.de

postal address:

Bavarian Natural History Collections
The Bavarian State Collection of Zoology
Dirk Neumann, Section Ichthyology / DNA-Storage
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81247 Munich (Germany)

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