Providing collection care, preservation and conservation treatment services to collectors and collecting institutions.
Vol.2 No.3 Winter 1999-2000 Exhibiting Without Damaging Collections
Exhibiting without damaging collections
by Helen Alten
After 34 general conservation assessments a pattern has emerged: the smaller the institution, the larger percentage of its collection is on permanent display. County historical societies display 75 to 95 percent of their collection. By contrast, larger institutions display five to 20 percent of their collection. In every museum there is a disproportionate amount of space dedicated to exhibits. The ideal museum's space allocations should be around 40:40:20. Forty percent exhibition halls, 40 percent collection storage space and 20 percent staff offices, theaters, education rooms and programming spaces. But smaller museums have as much as 80 percent of their space dedicated to exhibits. As collections grow, additions are built for more exhibit space, while storage continues to be crammed in hot attics, damp basements or small closets. Eventually, most museums will realize that permanent exhibits of the entire collection not only cause damage, but reduce repeat visits from the community. Exhibits become stale and financial support drops as a result. But until that time, with the vast majority of museum collections on permanent exhibit, it is imperative that the exhibits provide the least possible damage so the collection will last.
Exhibition by its very nature damages collections. Light fades and accelerates other deterioration. Objects are susceptible to vandalism and theft. Poor display techniques and materials cause physical distortion, staining, scratching, tearing and chemical reactions with fumes concentrated in enclosed spaces. Open exhibits require regular cleaning, which wears down artifacts. Open exhibits suffer from pests, dirt and temperature and humidity fluctuations.
Making the exhibit accessible includes planning for visitor flow, adequate and clearly marked emergency exits, and galleries that are easily accessible as required by the Americans with Disabilities Act (ADA). Also, plan for safe movement of collection materials in and out of galleries. To secure and preserve the collection, the gallery should have fire protection, a controlled environment and security systems.
Preservation includes providing adequate support for objects, using inert materials to construct exhibits and designing exhibit areas to deter theft and reduce light damage. For example, leather, textiles and paper items distort without support. Sheet music on a pump organ slumps unless there is a rigid acid-free board support behind it.
Preservation means not altering an artifact. Exhibiting should not stain, tear or make holes in a piece. Too many museums still nail or pin, glue and tape collections. Tapes, glues, oil-based products (varnishes, paints, clays) and sticky clays permanently stain most artifacts. Thumbtacks, sewing machines and nails make irreversible holes. Unpadded hooks, nails, fishing line and wire scratch surfaces. Corroding metal stains surfaces. Some materials deteriorate to form fumes that will weaken, stain and damage artifacts.
When planning an exhibit, consider visitor flow, environmental risks, artifact rotation, maintenance ease and the time required for preservation activities prior to opening. Make sure staff can change lights, filters and sensors and rotate art or artifacts on a regular schedule. Paint and other coatings need time to cure. Plan time for mannequins or special mounts to be constructed and conservation treatments.
Exhibit planning and maintenance is easier with written guidelines. Eventually, each museum should have written policies for light levels, photography, use of plants, object rotation schedules, acceptable mount materials and techniques, temporary exhibit guidelines, disability considerations, and basic security measures for people and collections.
Disability and Design
Exhibit heights are critical. When standing the average adult's line of sight 67 inches. The average for someone in a wheelchair is 48 inches. Flat art on the wall should be displayed between 48 inches and 67 inches from the ground. For accessible viewing, an exhibit case's base should be no higher than 36 inches. The bottom of a table case should be exactly 27 inches from the floor, allowing knee space for a wheelchair user while still noticeable by a visually impaired visitor using a cane. A protrusion above 27 inches will not be "seen" by a cane user. To warn the cane user of a protrusion above 27 inches, place something on the floor below.
Lengthy exposure to visible light causes fading and weakening. The conservation rule of thumb for over 20 years, based on Garry Thomson's The Museum Environment, has been five footcandles for three months per year to display light sensitive materials such as color photographs, textiles and watercolors. Raise the lights levels to 15 footcandles for less light sensitive materials such as oil paintings. However, this rule of thumb is too simplistic. Not only are some oil painting colors extremely light sensitive, altering within two years at five footcandles, but older visitors may require higher light levels for clear viewing. The Smithsonian Guidelines for Accessible Exhibition Design recommends an ambient light level of five to 30 footcandles in a gallery. Text panels, displayed artifacts, ramps, stairs and pathways should be lit from 10 to 30 footcandles. Directional signage should be slightly brighter, lit at 20 to 30 footcandles. If light levels are raised in a gallery for ADA, then limit collection exposure to 5,000 footcandle hours for sensitive watercolors and textiles and up to 16,800 footcandle hours for less sensitive materials, traditionally thought of as painted wood and oil paintings. For example, if exhibit lights are raised to 30 footcandles and the museum is open seven days a week for 10 hours each day, a watercolor should be left on exhibit no longer than 16 days each year. The Canadian Conservation Institute's Light Slide Rule suggests that visible light damage would occur to the watercolor after four months on exhibit.
To extend exhibit time, place timed switches next to cases. Visitors raise light levels only when viewing, then lights drop to a low or nonexistent level when the viewer is finished. Monitor the cumulative light level with a light reading datalogger such as the Hobo (Onset Corporation). Use a light meter to install and check exhibits.
The visitor's ability to read labels affects their perception of gallery light levels. Use large clear fonts for exhibit labels and signs. Make sure the paper and ink contrast rather than blend. The best contrast is black lettering on a white background. Slant labels so they are easy to read and receive more light.
Purchase or borrow books about exhibit preservation issues. Invest in continuing education opportunities. Expand staff skills so that they recognize problem areas. In general, if a problem exists in an exhibit, block its damaging effects. Monitor to detect problems before they become serious. Respond immediately to a problem. And, if damage occurs, recover and treat the object.
NEH funds available to underserved regions?
The Extending the Reach initiative was launcehed last November. Fourteen state humanities councils were awarded $20,000 to develop a humanities project with at least two partner institutions that can serve as a model for collaborative work in the humanities.
The National Endowment for the Humanities (NEH) announced public grants in its Extending the Reach initiative this February. The Initiative is designed to increase the quantity and quality of cultural programs in underserved regions of the United States and at underserved institutions of higher education.
The targeted regions are Alabama, Alaska, Florida, Idaho, Louisiana, Missouri, Montana, Nevada, North Dakota, Ohio, Oklahoma, Texas, Washington, Wyoming and Puerto Rico.
Targeted institutions of higher education are historically black, Hispanic-serving, and tribal colleges and universities.
Under Extending the Reach, NEH seeks applications from schools, humanities organizations and film and radio producers in the designated states and territory and from the designated colleges and univesities.
Extending the Reach program descriptions, application guidelines, and contact information are now posted on NEH's website at http://www.neh.gov/grants/extending.html.
For state/territory inquiries contact Karen Mittleman, 202/606-8631, firstname.lastname@example.org. For inquiries regarding historically black, Hispanic-serving, and tribal colleges contact Fred Winter, 202/606-8287, email@example.com.
Online Grant Bulletins
To stay abreast of the latest funding changes subscribe to on-line newsletters produced by federal funders. These free bulletins provide regular information on funded projects around the country, current grant information and training opportunities.
An inexpensive method to heat seal Mylar
by Catharine Hawks
Polyester films, such as Mylar S or D are stable, clear and have a high melting point. These traits have led to their widespread use in making sleeves or envelopes to protect documents and other items in museum collections.
Equipment designed to seal these films with heat (e.g. polyester cross welders, and ultrasonic sealers) can be prohibitively expensive when needed for minor applications. The usual alternative to heat or ultrasound seals - the use of double-sided adhesive tapes - may not always be practical, especially for small sleeves or envelopes. When necessary, the following method can be used to bond Mylar film to itself. Keep in mind that melting a plastic can generate potentially toxic vapors. Perform the work only in an adequately ventilated area.
1. Align two sheets of 3-mil Mylar filn on a self-healing cutting mat that features an alignment grid. Place one sheet on top of the other.
2. Using a steel straightedge and the alignment grid as guides, cut the film with a razor knife to about 1/4 inch larger on each side than necessary to hold the label, document or other object that will be housed in the sleeve.
3. Use masking tape or duct tape to cover the edges of a standard pane of window glass.
4. Place the pane of glass over the grid on the cutting mat and place the precut Mylar on the glass.
5. Using a steel straightedge and the alignment grid as guides, gently run a heated soldering iron along three sides of the sleeve. Wear a heavy, heat-resistant glove on the hand that steadies the straightedge. (NOTE: Attaching a rheostat to the soldering iron will improve temperature control and the quality of the resulting seal. Mylar will melt in the 400-500°F range; however, most soldering irons are designed to achieve much higher temperatures than will be needed to melt the plastic.)
6. When the enclosure is complete, round all of the courners of the Mylar envelope or sleeve using small manicure scissors with curved tips.
Heat seals made in this manner are not especially strong, but will withstand reasonable handling.
Catharine Hawks is a conservator in private practice specializing in objects and natural history specimens. This technique was originally discussed in C. Hawks and S. Williams. 1986. "Care of specimen labels in vertebrate research collections." pp. 105-108 in Proceedings of the 1985 Workshop on Care and Maintenance of Natural History Collections (J. Waddington, and D. Rudkin, eds.). Life Sciences Miscellaneous Publications, Royal Ontario Museum, Toronto.
Polyester is polyethylene terephthalate. Mylar is a registered trademark of E.I. duPont de Nemours & Co., Inc.