Insect infestation in wooden icon

Anne Lane <alane [at] charlottemuseum__org> writes

>I received a heads-up today that I will be receiving a call
>concerning a possible insect infestation in a wooden icon. I am
>assuming it is painted on wood, possibly with gold leaf. I have no
>idea about its age, country of origin, etc. My question concerns the
>two major methods of treating insect problems that I am aware of,
>freezing and anoxia.

There are a variety of effective "poison-free" treatments now
available for killing insects. One can use heat (with or without
humidity buffering), cold, purging with carbon dioxide, nitrogen or
argon, oxygen absorption, or combinations of the above. However, the
simplest and most commonly used system seems to be anoxia using
oxygen absorbers and a flexible barrier film bag.

The system is used as follows: The infested artefact is placed in a
flexible bag made of a material that is impervious to oxygen (this
is usually a multi-layer plastic film, such as Escal).  An
appropriate quantity of oxygen scavenger / absorber sacjets (such as
Ageless) is added, and the bag is heat sealed closed. Over the next
few hours, the oxygen absorbers will remove the oxygen from the
trapped air, leaving almost pure nitrogen, and the original water
vapor. During the absorption process, a very small quantity of
additional moisture and a little heat are released by the oxygen
absorber. The warmth of the absorber packets are easily radiated
away and the amount of moisture released by the packets is usually
inconsequential when compared to the moisture buffering capacity of
the artefact itself.

As implied above, it is a good idea to be aware of other factors
which will hinder or speed the anoxic killing process: low
temperatures (above freezing) will slow the process--it is best to
keep the object at a slightly elevated temperature during the
treatment to ensure a thorough kill). Again, the buffering capacity
of the artefact will likely be able to cope with any small change in
the RH of the bag as the temperature is slightly increased.

All the systems mentioned call for maintenance of extreme conditions
of one sort or another, and all need to be carefully planned and
monitored. The advantages of anoxia using oxygen absorbers include
simple materials needed, and the relative ease of employing the
system--little or no attention is needed once the bag is sealed. The
primary disadvantage when compared to other systems is the time that
may be needed for treatment. Depending on the insect species and the
ambient temperature, it may be necessary to keep the artefact in the
bag for more than a month, or as little as a few days.

Further information can be found at <URL:http://www.keepsafe.ca>

Jerry Shiner
Keepsafe Microclimate Systems


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                  Conservation DistList Instance 21:65
                   Distributed: Sunday, June 15, 2008
                       Message Id: cdl-21-65-005
                                  ***