Humidifying nitrogen for anoxic treatment

Will Jeffers asked whether it was necessary to humidify the nitrogen
flush in a nondynamic Ageless fumigation of a Japanese folding
screen.  My off-the-cuff opinion is that humidification may not be
necessary, but buffering may be a wise precaution if the object
contains lots of air or is RH sensitive.

The final RH in a microenvironment for *passive* anoxia using
Ageless will be the cumulative result of a) the amount of dry gas
used for purging plus the RH of whatever residual ambient atmosphere
was not purged, b) the amount of moisture (EMC) in the object being
treated, and c) the moisture given off by the Ageless sachet when
the exothermic reaction warms its internal humectant.

Since, in a tight bag, a hygroscopic object will usually have a much
greater capacity for moisture than the surrounding air, the object
should be expected to "self-buffer" the microenvironment fairly
well. (This is of course not the case in an active system with
constant gas purging).   Also, since Ageless may elevate the RH
depending on the rate of its reaction (more O2 = more heat = more
moisture), dryer initial conditions may be safer.  Especially since
anoxia depends on dessication for its efficacy, and a high RH may be
ineffective.

What all this means is that too dry may not be a problem, but too
humid could be.  For this reason, the presence of excess dunnage
(wood, paper, cloth, silica gel...) is recommended.


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                  Conservation DistList Instance 13:39
                 Distributed: Monday, January 10, 2000
                       Message Id: cdl-13-39-002
                                  ***