Lon,
The problem with making air passages through acrylic vitrines is that they breathe in both directions. When the cases are warmed from sources of illumination air is forced from the case. When the lights go off and the case cools, air is sucked back into the cases... bringing with it dirt, dust, etc.
If you would like to vent the cases I would recommend creating a passage through the base of the case interior and loosely stuffing it with lamb's wool (available at your local pharmacy). This will permit some breathing, but from the interior of the base of the case, and through a filter material that can be easily cleaned/replaced.
The real problem here is not the cases, but the source of your illumination. If you're getting the kind of heat buildup that worries your conservators, you may well be over-illuminating or using the wrong light source. For specifics on over-illuminating, check with your conservator. The materials that are the most light-sensitive are going to require somewhere in the neighborhood of 50 lux illumination. You won't be having any heat build up at that level unless the lamps are inside the vitrine!
Where possible, you may wish to convert from incandescent lighting to encapsulated fluorescent with additional UV filtering acrylic sheet lenses on the fixtures. If you would like to contact me off-list regarding specifics, I may be of further assistance.
Dave Meyersburg
New York State Office of Parks, Recreation and Historic Preservation
Chief of Historic Sites Exhibits
Peebles Island Resource Center
Waterford, New York 12188-0209
518/237-8643 extension 3228
-----Original Message-----
From: Lori Tomlinson [mailto:[log in to unmask]]
Sent: Thursday, March 13, 2003 10:36 AM
To: [log in to unmask]
Subject: advice on exhibit case design
Dear Listers,
I’m looking for advice on exhibit case construction. We have recently designed and built new cases with removable plexiglass tops of varying lengths and heights. While the seal created by these cases is not airtight, there is potential for build-up of heat, humidity, etc. Artifacts displayed in the cases are protected from the base by a layer of chemically stable, acid-free material, but the artifacts may still contain acids, contaminants, etc. of their own. Small holes can easily be drilled into the plexiglass tops, close to where they meet the base, to allow for some airflow. Can anyone suggest if such holes should be added, and if so, how many, etc? Any other suggestions pertaining to these cases would be appreciated.
With many thanks,
Lori Tomlinson
Division Manager
Charlotte County Historical Center
Charlotte Harbor, Florida
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