Humidifying nitrogen for anoxic treatment

I'm currently evaluating the need to humidify the nitrogen flush in
a nondynamic Ageless fumigation of a Japanese folding screen.  Each
screen panel consists of paper applied over a cedar latticework
core, with the panels attached to each other by means of paper
hinges.

In the GCI publication Inert Gases in the Control of Museum Insect
Pests (1998),  Nieves Valentin's research regarding humidification
of argon, carbon dioxide, and nitrogen is summarized, with the
conclusion that,

   "...museum holdings maintained in modest relative humidity ranges
    can be easily disinfested using a nonhumidified inert gas.
    However, works of art already exposed to high humidities, and
    sensitive objects such as musical instruments or polychromed
    wood, should be treated with humidified gas."

The same GCI publication refers to anoxia treatments of Japanese
screens at the Los Angeles County Museum of Art in which conditioned
silica gel (50%) was used to control moisture.

In discussing moisture balance during nitrogen fumigation in Museum
Pest Management Seminar Notes (CCI, 1993, rev. 1996), Tom Strang
notes that,

   "organic objects contain sufficient reserves to safely
    equilibrate limited volumes of air... These objects will only be
    stressed when their buffering capacity is exceeded by too large
    a volume of gas or multiple exchanges of gas."

Strang suggests that if one is concerned about moisture balance, two
streams of nitrogen may be run at similar flow rates, with one
stream being run through a water bubbler to provide an approximate
50% RH when recombined with the dry stream.

While the pouch used for the fumigation of the Japanese screen can
be made to fit rather closely, the volume of gas contained in the
voids within the latticework will increase the overall volume of gas
within the enclosure. To humidify or not to humidify, that is the
question?

Any thoughts on this from the prevailing fonts of modified
atmosphere fumigation knowledge?

Will Jeffers
Collections Care Specialist
Department of Scientific Research
Museum of Fine Arts, Boston


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                  Conservation DistList Instance 13:38
                Distributed: Wednesday, January 5, 2000
                       Message Id: cdl-13-38-015
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