Heidi:
My friend J.Claire Dean, conservator, posted this
(excerpt) to the MuseumL list way back in 1995,
"Light Impressions is carrying a combined relative
humidity (RH) and
temperature indicating card. They are made up of the
standard blue/pink
colour scale and two strips that register temperature in
degrees F and
C."
As I read up on efficacy, they are good to +/-
5%, which in an exhibit case with a comparatively slow exchange of
air, these are entirely adaquate indicators of changes. That said, If
the artifacts are particularly sensitive to rapid RH changes, you should
look into the electronic devices.
Most types of paper, to my knowledge, will
not be affected much by a 5% change. The environment itself, ie: type
of wood the cases are made of, are far more likely to have an effect on
paper.
We have been using RH indicators for years in
traveling exhibits, and they have proven quite effective.
Hope this helps you in your decisions.
Tom Bennett
Exhibit Support, AK
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