Object Rotation in Exhibits

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While object rotation or substitution can be an excellent conservation tool, these procedures have practical implications that must be planned into the design and maintenance of an exhibition.

When are objects rotated or substituted?

The rotation of a collection object on and off exhibition, or the substitution of one collection object for another similar one, minimizes damage caused by long-term exposure to light and other environmental conditions. In addition to preservation benefits, objects on loan from other institutions may have to be substituted. The need to rotate or substitute objects during an exhibition depends on several issues:

• duration of the exhibit; rotation is rarely necessary when vulnerable materials are put on short-term display (3-6 months), unless the object is especially vulnerable or environmental conditions are very severe.
• vulnerability of the collection materials; a limitation on the length of display is most common for objects particularly vulnerable to display conditions. Such materials include textiles and hand tinted or dyed materials such as photographs or baskets.
• display conditions; the actual risk of exposure can be limited by modifying the display conditions (open versus closed display; dust filtration, light levels, etc.).
• inherent value of the object; the curator must determine if damage to an object from long-term display is acceptable. Depending on the collection, it may be better to sacrifice one object to long term display rather than to allow slighter amounts of damage to multiple objects.
• personnel to implement policy; there must be a qualified staff person to implement the scheduled rotation or substitution. The conservation benefits of rotation or substitution can be out-weighed quickly by poor object handling.
• availability of substitute objects; objects are often rotated with other collection objects.

Sometimes, however, reproduction materials or replicas are used. Two dimensional objects are more easily produced, while three dimensional materials are often more difficult and costly to replicate. The purchase of period or similar "non-collection" objects can sometimes serve as a substitute, allowing the original collection object to be protected from over-exposure.

The Exhibit Object Rotation or Substitution Report Form can be used to administer a rotation or substitution policy. Major points in a successful policy are:

• adhere to the rotation or substitution schedule;
• minimize handling of the objects;
• insure that the initial standards of case seal and mounts are adhered to during rotation;
• provide appropriate storage conditions for objects not on display;
• document the condition of the objects at the time of the rotation or substitution.

How often should objects be rotated or substituted?

The period of time that an object should remain on exhibit is dependent on many factors. In general, objects remain on exhibit for a period of time dependent on the conservation criteria and the exhibit design. Rotation and substitution schedules are an important part of the Exhibit Maintenance Plan and should be clearly related in this document. Depending on the circumstances, rotation of exhibit objects can occur every:

• three months
• six months
• nine months
• one year
• eighteen months
• two years
• five years

Different objects within the same exhibit may require different rotation schedules. While the benefit of imposing one schedule is clear, the display period for objects that are highly sensitive should not be extended to coincide with rotation of other objects that can remain on exhibit for longer time periods. A successful strategy for some museums has been to remove sensitive materials from display during periods of low visitation, which may account for periods of up to 6 months of each year.

What are the maintenance requirements for object rotation?

There are several practical factors involved in rotating exhibition objects. It is imperative that the case structure, and the location of the object within the case, allow for easy and safe removal and replacement. Plans to rotate or substitute an object(s) must be considered when designing and building the exhibit case.
Staff time is required to implement the changes. Decisions about the conservation criteria for an exhibit are sometimes based on the agreement that sensitive objects will be rotated on and off exhibit, or that a vulnerable object will be removed from display after a specified period. When the agreed upon schedule is not adhered to, objects suffer. The administrator of the institution, as well as the exhibits and curatorial staff, must commit to planned rotation and substitution.
Lastly, rotating objects can have an impact the exhibit's interpretation. The exhibit text and label copy must be general enough to allow for object content changes, or new text must be installed along with the object(s).