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Subject: Display cases

Display cases

From: Susan Bradley <sbradley>
Date: Thursday, November 25, 2004
Isobel Griffin <igriffin [at] nts__org__uk> writes

>I am interested to hear other people's experiences of controlling
>the environment inside display cases using mini air-conditioning
>units inside the cases. How well do the units perform, and can
>anyone recommend a particular manufacturer?

We have used control in individual showcases as the main means of
controlling RH for objects on exhibition since 1968 when Munters
dehumidifiers were installed in showcases for Assyrian copper alloy
objects susceptible to bronze disease.  Starting in the early 1980s
we built on this work and now most non-airconditioned galleries have
a few conditioned cases.  Initially we were installing small
humidifiers controlled by in-case humidistats to provide humidified
atmospheres for sensitive organic objects, or desiccant type
dehumidifiers to provide dry environments for sensitive metal
objects.  In taking this approach we accept that there will be a
summer peak and a winter trough in RH.  When we put Lindow man on
display we fitted both a humidifier and dehumidifier under the case
controlled by a single humidistat.  All of these systems worked well
in that no observable damage has occurred to the objects and the
environments have been  within the tolerances required.  The main
problem we get is people forgetting to fill up the humidifiers.

In the last 10 years we have started controlling RH using an in-case
system supplied with the showcases by one of the showcase
manufacturers we use, Glasbau Hahn GmbH.  These units work on a
peltier system and can control a wide range of set RH for one case,
or remotely for several cases.  In one gallery we control cases for
glass susceptible to weeping with individual units, in another we
have one unit supplying conditioned air to 10 cases.  In the
recently opened Wellcome gallery the four double height cases are
controlled to a tight tolerance by a remote control system.  We
have found this a reliable and cost effective approach.  Other
companies make similar systems but as we have not used them I cannot
comment on them.

Susan Bradley
Head of Conservation Science and Analytical Chemistry Group
Department of Conservation Documentation and science
The British Museum
Great Russell St
London WC1B 3DG
United Kingdom
+44 2073238679
Fax: +44 2073238636

                  Conservation DistList Instance 18:25
                Distributed: Wednesday, December 1, 2004
                       Message Id: cdl-18-25-001
Received on Thursday, 25 November, 2004

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