Foam deformation during pest treatments with nitrogen

Julianne Phippard <jphippard<-a t->britishmuseum< . >org> writes

>We are about to begin commissioning and testing our new anoxic pest
>treatment chamber which will use a nitrogen generator.  We are aware
>of experiments performed by the Winterthur Museum regarding the
>deformation of different foams during pest treatments with CO2, but
>we do not know if this would apply to treatments with nitrogen.  Has
>anyone encountered problems with foam objects, mounts or supports
>such as deformation or reduced compression resistance after
>treatment with nitrogen?

During nitrogen treatment, nitrogen will not alter the chemical
composition of any material--nitrogen is inert under atmospheric
pressure, and normal air already contains 80% nitrogen.  In that
sense it is also irrelevant whether the nitrogen you use for your
chamber comes from a cylinder or is generated on site.  However, PU
foams are generally quite unstable, and it may be that there is a
different factor that will affect the foam objects etc.

I had a chat with Jan Hoffmann, the conservator at Landesmuseum
Hannover

    <URL:http://www.landesmuseum-hannover.niedersachsen.de/portal/live.php?navigation_id=24291&_psmand=183>

They have 10 years of experience with their own nitrogen chamber.
Jan says nitrogen treatment is a complicated process, with the two
factors most often affecting objects in their treatment chamber
being temperature and humidity.

Ideally you would be able to undertake the nitrogen treatment under
slightly elevated temperature to stimulate the metabolism of the
insects you are trying to kill to decrease the amount of treatment
time.  However, PU foam does tend to become brittle or sticky under
elevated temperatures; at the same time, the PU foam emits VOCs that
can contaminate other objects which are in the treatment chamber at
the same time.

You also need to control the RH in your treatment chamber,
especially if you are increasing the temperature, as elevated or
decreased RH can result in all sorts of damage to your objects.  Jan
also confirmed that damage due to nitrogen exposure is extremely
unlikely.

Christian Baars
Senior Preventive Conservator
National Museum Cardiff
Cathays Park
Cardiff CF10 4NP
+44 29 2057 3302


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                  Conservation DistList Instance 28:24
                Distributed: Thursday, November 13, 2014
                       Message Id: cdl-28-24-003
                                  ***