Stuffed specimen and hygrometry

In the Natural Sciences Museum (Brussels) I am currently facing a
conservation issue. Relative humidity is decreasing steadily in one
showcase; the conditions in it are now really too dry.

A historical stuffed animal (stuffed in 1871) is on display for 3
months in a new showcase (+/- 1.5 to 2 cubic meters; front = glass;
walls = laminated MDF).

The showcase has 2 Art Sorb cassettes in its right wall; the holes
through the wall (between the cassette container and the showcase)
were made according top the Art Sorb instructions manual.

The showcase includes only LED lighting; furthermore the LEDs are
switched off when no visitor is in the neighborhood.

The showcase is currently quite air-tight; hygrometry fluctuates
only by 3% in one day (35% min., 38% max.) Temperature is fairly
stable (18 - 20 deg. C).

Hygrometry and temperature are recorded using a Hanwell ml-4106
instrument. Records are computer-read. Values displayed on the
instrument panel comply with recorded values. Mean hygrometry is
steadily decreasing (+/- 45% relative humidity on November 18, less
than 35% on December 4, 2008).

Has anyone experienced something similar? Is the instrument we use
known to be reliable? What is the Art Sorb's behavior? Is it
possible that it would absorb "avidly"? Can the stuffed specimen be
highly hygroscopic (absorbing humidity from the atmosphere)?

Gerard Cobut
Biologist, museum developer
Museum of Natural Sciences
Exhibition development
Rue Vautier 29
1000 Brussels
Belgium
+32 2 627 42 44
+32 476 74 64 45
Fax: +32 2 646 44 33


                                  ***
                  Conservation DistList Instance 22:35
                 Distributed: Monday, December 8, 2008
                       Message Id: cdl-22-35-019
                                  ***