Since 1951, the Charters of Freedom have been safely contained in helium-filled, glass and metal cases built by NIST (then known as the National Bureau of Standards). For nearly as long, the Declaration of Independence, the Bill of Rights, and pages one and four of the Constitution have been on public display, attracting more than a million visitors annually to the Rotunda of the National Archives in Washington, D.C. From July 4, 2001 to Sept. 17, 2003, the Rotunda underwent extensive renovations, which now allow all six pages of the Charters to be on display.
An examination of the Bill of Rights and the Declaration of Independence in 1995 revealed signs of deterioration in the encasements' glass, although the precious documents were not in danger. Corrective improvements were deemed impractical because the cases are soldered shut and cannot be opened without compromising the seal. Subsequently, NARA concluded that new technology could enhance preservation of the founding documents. At the same time, NARA officials decided that new encasements should be designed to enable the flexibility needed to accommodate future advances in preservation methods.
In addition to building new encasements, NIST experts designed, built, and operate the extraction system that was used to remove the gases inside the former encasements without disturbing the documents—an intricate procedure that took several days of preparation. With collaborators from NASA, they analyzed the gases, which provided essential data on conditions and reactions inside the old encasements. Since parchment is made from animal skin, a key question is whether so-called out-gassing by the biological material would alter the chemical environment inside the encasements.
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