NASA identifies threat to documents

Encasements found to hold more water vapor than they should

May 31, 2002|By Michael Hines | Michael Hines,KNIGHT RIDDER/TRIBUNE

NEWPORT NEWS, Va. - A method of protecting the U.S. Constitution, Bill of Rights and Declaration of Independence may have posed the biggest danger to the historic documents, NASA Langley researchers say.

A NASA Langley-led research team that has been studying the problem since 1998 has found that conditions inside the encasements holding those documents was key in their potential deterioration. The chief problem, the researchers found, was that there was twice as much water vapor as there should have been.

Too little water vapor would have made the sheepskin parchment brittle. Too much could have caused it to decompose, said Joel Levine, senior research scientist in atmospheric sciences at NASA Langley Research Center.

Researchers had expected to find 25 percent to 35 percent relative humidity inside the encasements. Tests found as much as 60 percent.

The excess moisture likely came from the paper used to keep the documents from touching the back of the glass encasements. "No one really cared about the backing paper" when it was first installed in the 1950s, Levine said, "but the backing paper turned out to be the culprit."

Researchers also think the increased moisture caused white flakes to form from the glass, which actually sparked concern about the documents' welfare to begin with.

NASA Langley's involvement started because of a search for old air.

St. Mary's case

In 1992, Levine and other NASA Langley researchers joined excavation efforts in Maryland's historic St. Mary's City, where three lead coffins had been found. NASA Langley researchers hoped the coffins had been made airtight because of the lead, trapping pre-Industrial Revolution air inside. They hoped the coffin air would provide a good benchmark to compare how man has affected global conditions.

In 1998, researchers from the National Archives were looking into growing concerns about the historic documents.

The documents are sealed in containers containing humidified helium, and many experts feared the helium had leaked and allowed air, which is more volatile and reactive to enter. The appearance of the white flakes led many to theorize a chemical process had begun between the casing atmosphere, parchment and glass.

Margaret Kelly, research chemist for the National Archives, was looking to test conditions inside the frames and came across Levine's coffin work. She asked for help and was surprised when the center agreed without requiring the archival agency to pay for the work.

"They were doing it out of patriotism," Kelly said.

3 research teams

Three research teams have tested the encasement conditions, using methods normally used for aerospace research, such as a laser that detects what compounds are in the Earth's atmosphere.

There weren't any helium leaks. Just a couple of surprises.

In addition to the excess water vapor, researchers found high levels of carbon dioxide, about 10 times what's in Earth's atmosphere.

Both findings point to the backing paper, Levine said. Researchers believe that even the dry paper, which is made of a material rich in carbon, contained a high concentration of water vapor.

Over time, that vapor naturally dispersed within the encasements.

The documents were taken out of public display in July 2001.

The National Archives is set to put the documents in new encasements, and the NASA Langley research will help ensure there aren't adverse effects during the move.

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