Wood borer infestation

Following on the topic of treating pest infestation by freezing and
the survival of deathwatch beetles--the procedures used by museums
in this area are

    1.  If the freezer is a commercial type, which can reach
        temperatures below 30 deg. C, then a single episode of
        freezing, long enough for the core of the object to reach
        that temperature and remain there for two or more days, is
        used

    2.  If the freezer is a domestic type and only reaches
        temperatures between -20 and -30 deg. C then the object is
        given a freeze-thaw-freeze cycle, with several days at the
        freeze stage. e.g. small items might be put in the freezers
        for 3 days, allowed to thaw for 2 days and then returned to
        the freezer for 3 more days. The belief is that the thaw
        stage will encourage any eggs to start developing, making
        them susceptible to the second freezing cycle even though it
        is not below -30 deg. C.

We suspect that the samples with the deathwatch beetles were not
frozen for long enough, but unfortunately this process was carried
out some time ago, before records were kept of freezing. I need
hardly add that all items are wrapped securely in acid-free tissue
and polythene sheet which is sealed with tape, after eliminating as
much air as possible and that a careful watch is kept when the items
are defrosting to make sure there is no condensation forming inside
the enclosure.

Any comments and further advice on freezing methods welcome,

Helena Jaeschke
Conservation Development Officer
+44 1392 665951
Royal Albert Memorial Museum
Queen Street
Exeter EX4 3RX


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                  Conservation DistList Instance 21:9
                   Distributed: Friday, June 8, 2007
                        Message Id: cdl-21-9-014
                                  ***