The very first Magna Carta dates to 1215, when English barons forced King John to write down the traditional rights and liberties of the country’s free persons. A copy of the Magna Carta signed by King Edward I in 1297 currently resides within a helium-filled casement at the National Archives Building in Washington. But the medieval document is scheduled for a temporary removal in 2011 so it can be re-measured for a new case filled with argon.
Researchers worried that helium atoms, which are relatively small, could escape from the case holding the Magna Carta, leaving the 713-year-old animal skin parchment susceptible to degradation. Those fears proved unfounded, but the National Archives has chosen to preserve the parchment in another inert gas, argon, whose larger atoms have proven easier to contain.
“Argon is used to displace oxygen and any moisture that may be remaining in the encasement area, to preserve the document and minimize degradation,” said Mark Luce, an engineer at the National Institute of Standards and Technology.