Receiving objects from tropical climates

Karen Potje <kpotje<-at->cca<.>qc<.>ca> writes

>How can we prevent damage to hygroscopic objects when the climate of
>origin of the objects is incompatible with the receiving climate
>(going from hot and damp to the recommended museum conditions) and
>when the objects are too big for vitrines or are not intended by the
>artist to be placed in vitrines?
>
>Also, does anyone out there have experience in using silica gel in
>crates or other packing methods to prevent objects from developing
>mould during long ocean transport?

I can offer two solutions that may be useful to you, especially if
combined.  Both use controlled microclimates and techniques proven
in both museum and industrial applications.

    To extend shelf life and prevent mould, food products are often
    packaged in anoxic environments.  This can be simply done by
    making an appropriate "bag" out of a multi-layer barrier film
    (such as Escal), and adding oxygen scavengers (such as Ageless).
    Although this will not kill mould spores, it will prevent (or
    dramatically slow) the growth or development of mould.

    To assist in the acclimatisation of the moisture-filled
    artefacts upon arrival, a series of stepped rh environments can
    be used to gently reduce the moisture content of the artefacts
    by exposing them to increasingly drier conditions.  This can be
    done by isolating the artefact(s) in any air/moisture tight
    enclosure, such as a sealed cabinet, a plastic tent, or the
    barrier film bags used for anoxic shipping.

The air flow from a microclimate generator (a unit that can deliver
a constant humidity and constant volume flow, such as the Mini One)
can easily be directed into the enclosure.  The humidity of the air
flow can be reduced as needed to slowly allow the artefact to
release moisture in a controlled manner.  Monitoring the moisture
content of the artefact's surface can be easily done by shutting off
the microclimate generator's flow for a few hours, and noting the
resulting humidity in the enclosure.

Some caveats: The process takes time--the moisture from deep inside
the artefact may take some time to migrate to the surface.
Measurement and instrumentation could be a challenge.  Consider
using facsimile wooden objects made of the same materials as the art
objects (these could be supplied by artist).  With facsimiles, you
can easily directly measure, determine by weight, or use invasive
methods for determining moisture content.

It is possible that damage will result no matter how gently you
change the artefact's moisture content (to match your "ideal"
environment)!  There have been many studies on the effects of
humidity and temperature on wooden sculptures in European churches.
They elucidate the processes of moisture uptake and release, and
document the wood's reaction to changes in humidity.

As to using silica gel: Using dry silica gel or other desiccant
while shipping could "shock" the artefacts if the desiccant absorbed
too much water too quickly.  Using preconditioned buffering (such as
Prosorb) preconditioned to 55 or 60% *might* prevent mould growth,
but barrier film shipping enclosures would still be necessary.
Also, the appropriate application of buffering, and the consequent
results would be prone to many mitigating factors.

In summary: Anoxic packaging should prevent the growth of mould
during shipping.  Slow and measured acclimatisation might prevent
damage from environmental changes, and could be integrated into the
receiving process by feeding a flow of air at appropriate humidity
levels into the anoxic shipping envelopes upon receipt of the
objects.

Jerry Shiner
Keepsafe Microclimate Systems
416-703-4696


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                  Conservation DistList Instance 28:32
                 Distributed: Friday, January 16, 2015
                       Message Id: cdl-28-32-003
                                  ***