The Charters of Freedom, the official copies of the United States Declaration of Independence, Constitution and Bill of Rights, were hermetically sealed in 1952 in glass and lead encasements filled with humidified helium. Deterioration of the inside glass surfaces has become evident in recent years, and is believed due to elevated water vapor concentrations, which can also be a direct threat to the parchment documents. The National Archives and Records Administration and the National Institute of Standards and Technology have undertaken to construct new encasements that will keep oxygen concentrations below 0.5% over 100 years, maintain a stable humidity level, and include mechanical and broadband optical access for gas sampling and spectroscopic monitoring. Prior to disassembly of the existing encasements, gas samples are extracted for humidity measurement and mass spectrometric analysis. This project presents several difficult vacuum technology challenges, including hard-sealing large glass windows to lightweight structures (for public viewing of the documents), helium leak testing the sealed encasements without evacuation, measuring humidity of small-volume gas samples, and extracting clean samples from the small-volume solder-sealed encasements. In all cases the solutions are constrainted by the absolute necessity to avoid perturbing the documents or over-stressing the lightweight encasements. To date, the gas sampling and reencasement process has been carried out for three pages of the Constitution. This talk will describe the vacuum techniques used and present the experiences and results to date.