Guideline10.1: Enclosures are used whenever possible and are always used for vulnerable exhibit objects.
Why is closed display always recommended for protection of exhibit objects?
Over the past century, museum experience has taught us that conservation is greatly enhanced when collections are housed in enclosures. “Open exhibition” introduces a host of hazards that ultimately complicate preservation efforts. (Any group of objects displayed without protective enclosures can be defined as an “open exhibit.”) Even when the hazards of dust, improper humidity and temperature, pests, and light exposure are mitigated on a building-wide scale rather than through individual cases, an enclosure will always provide objects with greater protection from theft, vandalism, and physical damage than will open display. And the most stringent protection can be achieved most effectively through a specially-designed exhibit enclosure.
A detailed discussion of case design is provided in Standards **. However, an overview of enclosures and their characteristics is provided here to assist with decision-making.
What are the conservation advantages of well-designed and carefully fabricated Display Cases?
Although display in cases is the norm for most museum exhibits, the benefits of enclosure are rarely calculated methodically. When designed appropriately, an exhibit case can protect its contents from most forms of physical damage and deterioration. To be most effective the design has to be thought out systematically—the case should be designed with the appropriate level of protections for the particular hazards that are of concern; and the case has to be effectively integrated into the exhibit environment so that building features such as vents and lighting do not interfere with case functioning (see Standard *).
- Security: The barrier of a case provides a certain level of physical protection from handling and incidental touching. Furthermore, a wide range of security options can be designed into an exhibit case, including vandal and theft resistant security glazing, dual locking systems, and case alarms.
- Fire and Water: Well-sealed cases provide protection from heat and smoke. And depending upon the construction materials, a case can provide fire resistance. The seal of the enclosure and the design of the roof or case ceiling can also prevent water damage.
- Contaminants: A case provides the optimum level of protection for objects that are susceptible to damage from dust and contact with foreign particulates. Air filters should be incorporated in ventilated case designs or the exhibit case should be sealed sufficiently to restrict airflow and prevent particulates being drawn inside. The inclusion of pollutant absorbent materials can protect sensitive objects from chemical contaminants.
- Pests: Tightly sealed cases prevent or deter pest infestation. Insect entry routes follow airflow, but gaps measuring smaller than 0.3mm prevent the entry of almost all museum pests.
- Climate: Well-sealed cases fabricated with moisture resistant materials can protect humidity-sensitive objects by buffering them from the constant fluctuation of relative humidity. Because the rate of air exchange is decreased, the environment inside the case can be stabilized, protecting objects from the excessive ambient humidity swings. The inclusion of silica gel and other climate control products can stabilize the humidity level within a sealed case in exhibit spaces with little or no humidity control.
If desired, a case can also provide temperature control. However, this is not generally necessary.