There are at least two considerations to this question.  The first is if dropping the building temperature below freezing would kill insect infestation in the collections.  The answer to this is NO.  In order to kill pests with freezing, the temperature must be dropped below 0 F quickly, held there for a period of time, then warmed for a short while, then dropped quickly again below 0 F and held there for a period of time.  It is simply not possible to drop the temperature fast enough within the entire building, nor is it likely that the temperature would fall low enough.  Remember, in nature, these pests regularly survive winters when nighttime temperatures can be well below 0 F.  The necessary missing ingredient is rapid temperature drop, which must be much faster than occurs from wintertime day to night.

The second consideration is the effect of low temperature on collections.  This is moot for the purposes of this question, as the process would be ineffective at insect kill.  In general, low temperatures are safe for many types of collections materials.  The primary exceptions are paints and varnishes, or any materials containing them.  As contained in the Mecklenburg article referenced by another poster, the key is the glass transition temperature for these materials.  For acrylic paints, it is recommended that the temperature not fall below 55 F.  Oil paints probably can go lower, to about 40 F, without damage.  

In looking at preservation of collections, there are always conflicts.  For many materials, low RH caused by human comfort temperatures are much more damaging, and lower temperatures would result in higher RH and better preservation.  Each collection needs to be considered individually to determine the best combination of T and RH for overall preservation.  This is especially true when HVAC systems can not be used for full T and RH control, such as historic buildings.  

Marc Williams, President

American Conservation Consortium, Ltd.


---- George Harris <[log in to unmask]> wrote: 
> Hello,
> The collections manager at my museum thought that when we have our furnace
> replaced early next year that it might be a good time to let the building
> freeze to try and kill any pests that are in the collections.  I think it
> is not now going to happen, but some responses she got from a posting on a
> different listserv said that it wouldn't hurt the collections to have them
> be frozen.  This is completely wrong for some types of collections, of
> course.  Are there any resources that anyone can suggest that show how
> tempreature changes alone and tempreature in cunjunction with its
> relationship with relative humidity can damage collections?
> 
> Thank you.
> 
> Beau
> 
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