The U.S. National Archives in Washington D.C. prepares to return its copy of the 1297 Magna Care to public display, they have released a short documentary video, “The Encasement of Magna Carta,” which details its state-of-the-art encasement. The Magna Carta will go back on display on February 17, 2012. The video is part of the ongoing series Inside the Vaults.
The video shows the fascinating behind-the-scenes creation of the case which will display the 715-year-old document for the world’s viewing. The 1297 Magna Carta being encased is one of only four remaining 1297 originals. Magna Carta is said to have influenced early American settlers and been an inspiration for the Constitution of the United States.
This copy of the Magna Carta is on loan to the National Archives from its owner, philanthropist and co-founder of the Carlyle Group, David M. Rubenstein. Mr. Rubenstein underwrote the conservation treatment of the document and the fabrication of its new encasement. The encasement was designed by the National Archives in cooperation with the National Institute of Standards and Technology (NIST) who fabricated the encasement.
In the video, Mark Luce, director of fabrication services at NIST, Jay Brandenburg, project engineer and Charles Tilford, a physicist now retired from NIST, explain how the encasement was fabricated and assembled. Project manager Catherine Nicholson and supervisory conservator Terry Boone, both of the National Archives, discuss the conservation treatment and mounting of Magna Carta inside the encasement.
The encasement was machined at NIST out of two solid blocks of aluminum and sits on a unique cart designed to support the document on exhibit. The encasement is air tight and filled with humidified argon, an inert gas that unlike oxygen will not degrade the document. Elaborate instruments continuously monitor conditions within the encasement for humidity and evidence of leaks.
This is the second short documentary produced by the National Archives about Magna Carta. The first, “The Conservation Treatment of Magna Carta” can be viewed below:
“Inside the Vaults” is part of the ongoing effort by the National Archives to make its collections, stories, and accomplishments more accessible to the public. “Inside the Vaults” gives voice to Archives staff and users, highlights new and exciting finds at the Archives, and reports on complicated and technical subjects in easily understandable presentations. Earlier topics include the conservation of the original Declaration of Independence, the new Grace Tully collection of documents at the Franklin Delano Roosevelt Presidential Library, the transfer to the National Archives of the Nuremberg Laws, and the launch of a new National Archives user-friendly search engine. The film series is free to view and distribute on the National Archives YouTube channel.
Created by a former broadcast network news producer, the “Inside the Vaults” video shorts series presents “behind the scenes” exclusives and offer surprising glimpses of the National Archives treasures. These videos are in the public domain and not subject to any copyright restrictions. The National Archives encourages the free distribution of them.
Approximate Encasement Weight: 102 kg (225 lbs)
Approximate Assembled Dimensions: Length = 1041 mm (41 inches), Width = 743 mm (29.25 inches), Thickness = 162 mm (6.38 inches)
Encasement Environment – The encasement was sealed with an atmosphere of 99% highpurity argon, 1% high-purity helium, and an initial oxygen concentration of 1 part per million. The encasement seal achieved a very low leak rate that greatly exceeds the project requirements. The interior humidity ranges from ca. 40 to 42% relative humidity, depending on the temperature of the display area. This estimate was determined by measuring the helium leak rate and converting to account for the different permeation rates of helium and oxygen through the Viton seal material.
Seal – The compressive sealing pressure exerted by the glass and encasement body on the Viton O-rings is somewhere between 1.1 and 2.1 mega pascals (160 and 320 pounds per square inch), depending on the material properties of these specific O-rings (two concentric O-rings are used for the glass to metal seal). The gas pressure abutting the O-ring is atmospheric, approximately 100 kilo pascals (15 psi); air on the outside, argon and helium on the inside, and a time varying mixture of argon, helium, oxygen and nitrogen between the Orings.
Bolts – 32- 3/8” stainless steel bolts, spaced slightly more than 98 millimeters (3.88 inches) on center around the perimeter of the underside of the frame and sealing surface of the base. This provides an approximate seal pressure of 300 pounds per linear inch along the O-ring groove.
Frame – Monolithic 7075 aluminum alloy with a “dash black” powder coating finish for protection.
Base – Monolithic 7075 aluminum alloy with a black hard coat anodized interior finish.
Glass – Two 5 millimeter (3/16 inch) low iron glass (low iron) with 1.27mm (.05” inch) laminated interlayer that includes anti-reflective coating.
Platform – High-grade aluminum with holes spaced to provide moisture transfer between the humidified argon gas and the document, and a machined pocket in the profile of the wax seal.
Pockets – To reduce weight of encasement, strategic areas (or pockets) of material have been removed from the base, the document platform and the frame. In the base, there are 32 pockets along the side. In the frame, the 32 pockets are in between the bolt holes and are on the underside of the frame (concealed from view). The 36 pockets in the document platform are on the underside of the platform hidden from view.
O-rings – Two nested Viton 6.4mm (.25 inch) diameter o-ring seals run along the inside surface of the Base; one 2663mm (104.8 inches) and one 2972 (109.9 inches) long.
Source: US National Archives