Volume 18, Number 4-5
Aug-Sep 1994

Smithsonian Institution NEWS

From Office of Public Affairs, Smithsonian Institution, Washington, DC 20560

(202/357-2627; fax 202/786-2377)

embargoed for release: 10a.m. Aug. 21, 1994

Media only: William Schulz (202) 357-2627 ext. 116
Linda St. Thomas (202) 357-2627

Work of Smithsonian Scientists Revises Guidelines for Climate Control in Museums and Archives

Smithsonian researchers have found that museum objects can safely tolerate a wider range of temperature and relative humidity than previously believed. This new insight could save museums millions of dollars in construction and energy costs to maintain environmental conditions once considered essential for the preservation of artifacts.

The Smithsonian researchers, materials scientists at the institution's Conservation Analytical Laboratory in Suitland, Md., announced their conclusion about climate control in museums when results of some of their individual research projects were reported at a meeting this week of the American Chemical Society in Washington, DC.

The CAL scientists--Marion Mecklenburg, Charles Tumosa, David Earhardt [i.e., Erhardt] and Mark McCormick-Goodhart--reached their conclusion in the past year, during a series of investigations of the chemical, physical and mechanical properties of materials common to a wide variety of museum objects: anything from natural history specimens and archaeological artifacts, for example, to 19th-century landscape paintings, and photographic prints and film.

"As scientists, we don't work from the idea that each object in a museum is unique," Mecklenburg says. "Rather, we start by looking at the whole picture--examining and understanding all of the materials found in the vast majority of museum objects."

Previously, "ideal" environmental conditions for museums and archives had been set at 21 degrees Celsius (70 degrees Fahrenheit) with 50 percent relative humidity. Now, Mecklenberg [i.e., Mecklenburg] says, there can be as much as 15 percent fluctuation in relative humidity and as much as 10 degrees Celsius difference in temperature.

Through informal discussions of their work, the researchers say, came the understanding that materials such as wood, cellulose, various polymer coatings, fibers, minerals, pigments and the like share an overlapping range of tolerance to temperature and relative humidity. Within that range, the scientists say, any object--whether it's daVinci's "Mona Lisa" or an installation of Jeff Koons' vacuum cleaners--may be safely stored or placed on exhibit.

"Up to 50 percent of construction costs for new museums and archival storage facilities may go toward highly specialized heating and cooling systems," Mecklenburg says. "Our research shows that such specialized systems are unnecessary. Most museums can adequately protect their collections with commercially available technology, such as the heating and cooling systems used in grocery or retail stores."

Moreover, Mecklenburg says, specialized heating and cooling systems that keep temperature and humidity stable can be expensive to operate. Seasonal variations in temperature and humidity, particularly in temperate climates, he says, can mean monthly energy costs that soar to tens of thousands of dollars in order to maintain strict environmental controls. For older or historic buildings, he says, making use of conventional equipment avoids the structural damage that might result from installing precision heating and cooling systems.

The materials research at CAL that has led to the new insights about temperature and relative humidity involves laboratory tests of the properties (physical, mechanical, chemical) of materials commonly found in museums. The overall goal of the CAL researchers is to apply the best scientific knowledge about various materials to the treatment and conservation of cultural, historical, artistic and scientific artifacts.

At CAL, artists' paints, for example, might be cooled and dried to document responses to lowered temperature and humidity (too low, and many paints and coatings become brittle and crack). Other materials--wood, photographic emulsions, paper--are subjected to high humidity, or they undergo accelerated aging through exposure to many potentially damaging environmental factors, including heat, humidity, light and various pollutants.

The research applies not only to the museum environment, Mecklenburg and colleagues say. Research at CAL has pointed to the risk of cracking for acrylic paints if artwork is shipped in the cold and dry environment of an airplane's cargo hold, while mechanical stress tests show how paintings might hold up to the vibrations of a moving truck.

Computer modeling, the CAL scientists say, has given them another powerful tool for predicting or confirming what happens to materials under varying conditions. With today's advanced software, they can analyze the materials in complex objects--paintings, for example, wherein layers of different coatings and surfaces make impossible any meaningful laboratory analysis of how they will behave in concert.

"We can use computer models to see what should happen to materials under different environmental conditions," Mecklenburg says. "We build verification models to make sure it does happen. As we begin to understand materials more, we can let the computer take over to simulate a variety of different environmental conditions."

In general, the CAL researchers say, the low end of the temperature/relative humidity range prevents biological damage from microbial growth and minimizes chemical reactions that occur naturally within objects over time. At higher values for temperature and relative humidity, they say, physical damage is minimized.

"The work is capable of defining the tolerance limits of large classes of materials represented in museum collections," McCormick-Goodhart says. "It means we don't have to study every single object. That's the breakthrough."

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Note to Editors: A limited selection of 8x10 black-and-white prints is available from William Schulz in the Office of Public Affairs, (202) 357-2627 ext. 116. Visits to the Conservation Analytical Laboratory can also be arranged.