Temperature and Relative Humidity in Museum Display Cases-Wangda Showcase Limited

15 Feb

Maintaining acceptable levels of temperature and relative humidity in mueum display cases is very important. This will  help slow the rate of deterioration for the items on display just as it does for  those in storage. The guidelines provided in Basic Preservation Considerations  should be followed in determining acceptable levels.



What Are Macro- and  Micro-environments?


Acceptable levels of temperature and  relative humidity are controlled within a macro-environment, a  micro-environment, or a combination of both. The definitions of these terms seem  to vary within standard museum preservation practice. In general, the term  macro-environment refers to the conditions within a large space, such as the  entire display area, whereas micro-environment refers to the isolated conditions  within a smaller enclosed space, such as a display case.



What Are Active and Passive  Systems?


The conditions in the macro- or  micro-environment can be achieved by what preservation professionals refer to as  an active or a passive system. These definitions also vary in the preservation  field. As the terms are used here, active systems usually employ equipment such  as furnaces, boilers, air conditioners, dehumidifiers, and humidifiers. Passive  systems, on the other hand, usually rely on the natural buffering capacity of  materials such as paper, cloth, wood, and silica gel.



How Are Conditions  Maintained?


In practice, a combination of macro- and  micro-environments and active and passive systems is often utilized to maintain  acceptable conditions. The temperature and relative humidity of the entire  display area—the macro-


environment—are maintained by the  building-wide heating and air conditioning equipment—an active system. For  highly sensitive materials, such as metals that corrode in high humidity or wood  that shrinks in low humidity, a humidity- buffering material such as silica  gel—a passive system—is used in a display case—a micro-environment—to adjust  conditions and maintain them at the special levels needed by especially  sensitive materials. If you expect to loan items to a  museum in another geographic area where the conditions are very different from  those to which your items are acclimated, you may need to use a microenvironment  with a passive system. The same is true when borrowing items that you need to  protect while they are in your care. Do not hesitate to consult a preservation  professional for guidance in this.





The temperature and relative humidity in the  display area should be monitored just as in the storage area. The instruments  described in Basic Preservation Considerations can be used. Some of these are  available in small sizes that work well in display cases.

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