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Subject: Recording hygrothermographs and dataloggers

Recording hygrothermographs and dataloggers

From: Tom Dixon <tom.dixon>
Date: Thursday, February 15, 2001
For many years the NGV has used wind up recording hygrothermographs,
placed on stands to keep them at the level of pictures, to provide a
weekly record of environmental conditions in a selection of
galleries.  As we near completion of a major new building plus total
refurbishment of our main building, there is discussion as to
whether we should abandon these as antiques and replace them with
something far less obtrusive and less time consuming to operate.

Recording hygrothermograph charts are changed weekly but we also
have opportunistic day-to-day visual checks by security staff, other
staff members, passing conservators and members of the public who
have occasionally noticed a big spike and let us know (a rare
occurrence, but invaluable for prompt corrective action).  We also
use a variety of data loggers in travelling crates and sometimes
inside pictures, as well as compact dial thermohygrometers in show
cases, but in the former case we don't know there is a problem until
we download the information and in the latter, we can't see a record
of what happened when no one was watching.

I've found recording hygrothermographs especially valuable in
instances such as commissioning a new HVAC system, when things went
wrong at 2 a.m. and then seemingly corrected by 8, I was promptly
alerted to a problem and was thus able to track it down.  The
building engineers have a fully electronic system connected to a
central computer with hi-lo alarms which relies on data collected
from sensors in return air ducts.  This would seem ideal, yet
repeatedly these systems, or in some cases the operators, have
failed and it was only through our recording hygrothermographs we
were aware of a problem and, often against great resistance, were
able to convince building maintenance there even was a problem.

Recording hygrothermographs are time consuming to service and as we
gain exhibition space and go from two to three buildings, this will
increase significantly. They aren't great to look at, they can be in
the way in displays and they are not a cheap alternative to data
loggers or electronic sensors connected to a central computer.  I
certainly wouldn't want to buy more only to abandon them in a few
years.  However, trying to think through the available alternatives,
many of which are listed in the January AIC News in a comparison by
Rachael Perkins Arenstein, I still lean towards maintaining the
status quo simply because I and others can so easily see what has
been happening from this moment back until the chart was changed.

I would be grateful to hear from the list regarding positive and
negative experiences of replacing recording hygrothermographs used
for simultaneous monitoring of several large gallery spaces on a
long term and continuous basis with newer technology.

Thomas Dixon
Chief Conservator
National Gallery of Victoria
Melbourne Australia

                  Conservation DistList Instance 14:45
                 Distributed: Friday, February 16, 2001
                       Message Id: cdl-14-45-020
Received on Thursday, 15 February, 2001

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