Protecting the documents:
NASA taking great 'panes' to help Charters of Freedom weather time
Thursday, April 15, 1999
BY A.J. HOSTETLER
Times-Dispatch Staff Writer
After withstanding 26 amendments, a civil war and an impeachment trial
or two, the country's Constitution is getting some high-tech help from NASA
to battle the insults of time.
The U.S. Constitution (along with the Bill of Rights and the Declaration of
Independence) has spent the past four decades sealed in glass and bronze
display cases at the National Archives and Records Administration in
Washington. There, more than a million tourists each year file past the
18th-century documents, known collectively as the Charters of Freedom.
Each of the charters' seven pages has its
own case, consisting of a sandwich of
three panes of glass in a soldered frame.
The bottom pane is topped by a sheet of
cellulose-backing paper on which the
historic document rests. A thin glass
cover sits atop the parchment. Above
that is a narrow gap of space and then a
top pane of glass.
In encasing the documents, preservationists created a mini-atmosphere in each
frame. The frames were emptied of air and then filled with 1 percent water
vapor and 99 percent helium. The relative humidity was set at 35 percent to
keep the sheepskin parchment from becoming brittle. Helium was used to
prevent the corrosion that oxygen can cause.
At the time, the cases were state-of-the-art and seemed to work well for
many years, said Richard Judson, an engineer leading the National Archives'
re-encasement project. But several years ago, scientists began noticing
changes in the parchment documents, suggesting that time was taking its toll.
Areas of deterioration were found on pages two and three of the Constitution.
Conservators saw small cracks in the glass plates that hold the pages upright
for viewing, which could mean that outside pollutants were seeping in, and the
helium leaking out. Other problems suggested unwanted chemical reactions.
"The current encasements were starting to show signs of age," Judson said.
Correcting the problems isn't possible, because the cases cannot be opened
without compromising the seal.
Federal officials decided that it was time to move the papers. New enclosures
will hold the documents behind tempered glass in a titanium frame bolted
"The new encasements will look forward into the future," Judson said.
be state-of-the-art for several years to come."
The documents will be mounted within the frames so that glass doesn't touch
parchment. If necessary, archivists will be able to open the new cases. To
reduce the possibility of leaking, argon gas (which has larger molecules than
helium) will be used. Water vapor will also be added to create a 40 percent
relative humidity, which will help protect the documents if their cases are
A prototype of the new case design is being built to display the Constitution's
Letter of Transmittal sometime next year. Then, while the Archives' rotunda is
undergoing renovations, the other six pages of the Charters of Freedom will
be placed in their new homes for display when the Archives reopens in
Before the Constitution moves into its new home, however, officials at the
Archives wanted to know what was happening inside the cases protecting the
212-year-old parchments. They turned to scientists at NASA's Langley
Research Center, researchers more used to studying the Earth's atmosphere
than preserving historic documents.
The challenge was to sample the cases' atmosphere -- the level of humidity
and helium -- without breaking the seals.
"This was a once-in-a-lifetime opportunity," said Dr. Joel S. Levine, the
scientist who managed the project. "The U.S. Constitution is one of the most
important documents in the history of the world. It was an honor and a
privilege to be asked to perform this research."
Levine was tapped for the job last July by chemist Margaret Ann T. Kelly of
the National Archives, who knew about Levine's research in measuring and
analyzing the composition of atmospheric gases.
Last fall, Levine assembled a team of scientists to work on the Archives'
request. The team decided to adapt a laser system used in NASA's
atmospheric research program to peer into the encasements protecting three
of the five pages of the Constitution: the rarely displayed pages two and three
and the letter.
The system paired an instrument developed by Langley researcher Glen
Sachse, the diode laser hygrometer, with a process called spectroscopy to
sample the atmosphere without opening the cases.
Spectroscopy is the study of molecular structure through the absorption,
emission and scattering of light. Different molecules absorb the beams at
specific wavelengths. To study the atmosphere surrounding the Constitution,
the Langley team planned to test how the water vapor inside the cases
absorbed a tunable laser beam. The absorption would produce a particular
pattern, displayed on a graph, on a device called an oscilloscope.
That pattern could then be compared with one produced from tests of helium
and water vapor conducted at Langley. If the two patterns were identical, then
the cases had worked and remained sealed. If the patterns differed, then the
cases had leaked.
On Jan. 20, the Langley team assembled in Washington for the experiment.
While cameras from public television's NOVA rolled, Levine directed the
scientists as they tested the three documents and their encasements.
"These three documents are the basis for our government and many
governments around the world. To be in their presence for hours was very
impressive," Levine said.
When scientists aimed the laser at the edges of the cases, the water vapor
inside partially absorbed the beam. A comparison of patterns showed that the
cases' atmospheres had not changed. The Constitution was still protected by
the half-century-old helium and water vapor atmosphere.
For once in Washington, nothing had leaked.
"We could see [the results] in real time," Levine said. "Everything worked
flawlessly. What we showed is that these three encasements . . . remained
sealed for almost 50 years."
A day after the experiment, the laser system headed to the South Pacific,
where it is now aboard a NASA DC-8 aircraft to help scientists understand
how human activities affect the Earth's lower atmosphere. The flight is part of
the Pacific Exploratory Mission Tropics-B project, the fourth in a series of
NASA airborne missions to study the atmospheric chemistry of the western
and tropical Pacific Ocean regions.
Levine's team left Washington with two additional tasks. Before the charters
are moved, the Langley scientists will take atmospheric samples of all seven
pages. The samples will provide hints as to which documents might be
suffering damage to either the parchment or ink.
In addition, the team is providing tips to Archives officials on how to monitor
the atmosphere in the charters' new homes for the next 100 years. Although a
prototype encasement design was unveiled in March, one of the Langley
team's tips was incorporated just two weeks ago. Archives officials decided
to add small, "optical windows" of sapphire to the undersides of the cases so
that conservators can conduct regular laser tests of the atmosphere, Levine
The entire charters project will cost about $4.8 million, according to Judson.
About half of the cost, which is supported by an $800,000 grant from the
Pew Charitable Trusts, will pay for the new encasements.