In my opinion, the primary reason for artifact rotation is to protect
the artifacts on display from damage from environmental factors such as
light, dust, handling by visitors, poor temperature or humidity
conditions, pollutants such as sulfur that causes silver to tarnish.
Take your pick. But then, I am a conservator. Because such damage is so
specific to individual artifacts, even within similar categories (such
as textiles), it is very difficult to make general recommendations for
exhibits of materials. And as much as conservators would like to believe
that environmental factors alone determine artifact rotation, there are
also other factors to consider, such as the size of the staff to make
the changes, and the depth of the collection.

The primary materials that I recommend for rotation are textiles and
paper artifacts, and my main concern is light exposure, because light
has caused the most artifact damage at my museum over the past 50 years.
We make a great effort to rotate our textiles every two years. While
they are on exhibit, we keep the light levels around 7 foot-candle and
RH is also controlled, and we are only open 7 hours a day 6 months a
year for a total of about 1300 hours a year. We have arrived at these
conditions and this schedule by researching the relevant conservation
literature and working with curators, exhibit, and collections
management to determine a reasonable rotation schedule for everyone. In
general, everyone compromises to reach an exhibit period that maximizes
public access while minimizing artifact exposure. Even then, there are
exceptions to the rule. Some textiles are too light sensitive to be
exhibited for 2 years under these conditions, so they are rotated more
frequently. If curators want higher light levels, then they need to
consider shorter exhibits or more frequent artifact rotation.

To help make exhibit rotation decisions, one should be familiar with
recommended exhibit lighting and temp/RH levels for artifacts. Some good
sources for this information are: a CD titled Exhibit Conservation
Guidelines published by the National Park Service (check the website for
ordering information); Conservation Notes from the Canadian Conservation
Institute are also very helpful http://www.cci-icc.gc.ca/html/ or
http://www.preservation.gc.ca, ; or check out the Technical Lealets
available from the Northeast Documents Conservation Center at
www.nedcc.org.

The best advice I can give is to consult with a conservator who
specializes in preventive conservation. Once familiar with the
collection of artifacts you are planning to exhibit (including the
rotation pool) the conservator can make appropriate recommendations for
the long-term preservation of your collection.

Richard L. Kerschner
Director of Preservation and Conservation
Shelburne Museum
PO Box 10, Route 7
Shelburne, VT  05482
802 985-3348 Ext 3361

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