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NIST built two prototype encasements, which were tested extensively to evaluate the design and to analyze the performance and integrity of each component. The prototypes now serve as the back-ups that the National Archives hold in reserve, just in case.
Pressure and leak testing
Glass placed on the titanium frame will soon be bolted down to seat the seals. The blue protective film is removed during the later stages of assembly.
NIST experts on pressure testing, leak rates, and chemical analysis went to great lengths to make certain that the new encasements met NARA's demanding performance requirements. For example, they calibrated the pressure sensors and specified the components of the equipment system that purge the encasements of air and fill them with humidified argon. NIST researchers also developed an extensive leak testing protocol that is used to test the integrity of the primary seal. This same prescribed procedure may be used by NARA staff to test the seal periodically after installation of the documents.
Before installation of the charter pages, all encasements underwent full-system tests. In all tests, seal performance far exceeded the design requirement.
NIST also conducted studies to determine whether the encasement glass could withstand abrupt and large changes in atmospheric pressure. The prototype encasements were subjected to wide swings in pressure until the glass finally broke. "There are no known ways," researchers concluded, "that the encasements would see the level of pressure difference causing glass failure, except due to a gross error. . ."
Assembly
As the encasements were completed, they were shipped in special containers to NARA, where final testing and installation of the Charter pages was done. Several steps in the process are shown here:
NARA conservators prepare to put the transmittal page into a humidity chamber. The treatment raises the moisture content of the parchment, permitting it be flattened and dried under restraint to reduce distortions.
Credit:
Earl McDonald/NARA
NIST and NARA staff members prepare to place the titanium frame on the base of the encasement.
Credit:
Earl McDonald/NARA
NIST mechanical engineer Chris Evans adjusts the spectrometer situated outside two sapphire windows milled into the base.
Credit:
Earl McDonald/NARA
NIST engineering technician Mike McGlauflin and Richard Judson, NARA's manager of the Charters project, place the newly encased transmittal page into a cabinet for interim storage.
Credit:
Earl McDonald/NARA
Notice of Online Archive: This page is no longer being updated and remains online for informational and historical purposes only. The information is accurate as of 2001. For questions about page contents, please inquiries [at] nist.gov (contact us).
