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Subject: Vibration


From: Robert J. Koestler <rtkcc>
Date: Thursday, October 3, 1996
In response to Kaja Kollandsrud's request (in Conservation DistList
Instance: 10:29) for information on the effect of vibrations on

Much attention has been devoted to catastrophic failure of
collection mounting systems, and indeed building failure, due to
seismic events.  Little attention has been focused on the small
day-to-day vibration problems objects are subjected to while on

Some years ago I investigated problems of small pieces of wood
falling off objects in the Egyptian collection at the Metropolitan
Museum of Art.  The collection had been completely reinstalled over
the course of ten-plus years, with condition documentation and
conservation as needed.  After the installation, it was soon
observed that some of the objects were losing fragments of wood and
some had the appearance of dry-rot.  To assess for biodeterioration
I undertook a series of culturing tests for fungi, with ambiguous
results--most of the cultures were negative, while some had non-wood
attacking fungi--probably surface contaminates.  I followed this up
with wood cross-section analysis using TEM (this was kindly
undertaken by Dr. Robert Blanchette at the U. Minn.).  The cross-
sectional analysis revealed that the fragments were not undergoing
active biological attack (although evidence of historic attack was
found), but rather had been stressed as would occur if they had been
vibrated off the objects.  I then contacted a vibration expert at
Columbia University's Lamont Doherty Geological Observatory (Dr.
Klaus Jacobs) who was kind enough to come in with a crew of seismic
and chaos experts to measure for vibrations in our museum. The
results indicated that low levels of vibration (from air-
conditioning equipment and people traffic within the museum) were
being transmitted through the mounting systems of our objects.  In
some instances, the method of mounting enhanced the vibration
effects.  In the worst cases we followed up by measuring the
vibration frequencies transmitted through the objects and mitigated
those frequencies with appropriate padding material under the
pedestals or cases. We were able to reduce most of the vibrations
without re-doing the mounts.

Hope this helps,

Dr. Robert J. Koestler
Research Scientist
The Sherman Fairchild
Center for Objects Conservation
The Metropolitan Museum of Art

                  Conservation DistList Instance 10:34
                 Distributed: Thursday, October 3, 1996
                       Message Id: cdl-10-34-001
Received on Thursday, 3 October, 1996

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