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Feature: Preservation Materials Vol. 64, No.6 pp. 13-16
A Project for the Ages: Art, History, and Materials Science
Converge to Preserve the 1297 Magna Carta

Lynne Robinson
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The NARA team responsible for preserving the 1297 Magna Carta. (Left to right): Catherine Nicholson; Mary Lynn Ritzenthaler, director, Document Conservation Division; and Morgan Zinsmeister and Terry Boone, the senior conservators who will be performing the hands-on treatment to the document. (Credit: NARA)
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The Charters of Freedom on display in their new encasements. (Credit: Image by Earl McDonald for the National Archives )
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The performance of the seals is of primary importance for a long-term encasement. Onboard instruments located underneath the base allow the encasement atmosphere to be continuously evaluated for any potential degradation of the seals. (Credit: Eric Whitenton, NIST)
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This cross section model displays key elements of the Charters of Freedom encasements and demonstrates how they fit together. A monolithic base has been machined from aluminum and is fi tted to a titanium frame piece and laminated tempered glass window. A metal seal made from Inconel® alloy with a thin tin plating hermetically seals the encasement to keep oxygen out and prevent the protective inert gas from escaping. (Credit: Eric Whitenton, NIST)
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Installing the metal C-seal developed for the Charters of Freedom encasements. The project's criteria for a 100-year seal made the use of polymer seal materials problematic, prompting the decision to use metal seals. The seal of the glass to the base was particularly challenging and required a long series of experiments. (Credit: Eric Whitenton, NIST)
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The Waldseemüller map was the first world map to depict a separate Western Hemisphere, with the Pacific as a separate ocean. It also marks the first time that the word "America" was used for the newly discovered lands. (Credit: Library of Congress)
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The Waldseemüller map encasement, completed in 2007, presented significant design challenges because of its immense size. (Credit: NIST)
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One test performed on prototype encasements evaluates their performance under thermal shock. Brian Scace and Michael McGlauflin from NIST dump ice on a warm encasement to simulate being exposed to a hot building fire and then doused by ice cold water in an attempt to distinguish the flames. (Credit: Eric Whitenton, NIST)
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Jay Hendricks from NIST performs a series of glass breaking experiments on a prototype encasement with the laminated tempered glass used in the final product. It was determined that the glass developed for the Charters of Freedom project could handle up to five times the pressure anticipated in the worst case scenario prepared for by the design. (Credit: Eric Whitenton, NIST)
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Charles Tilford, NIST, performs leak testing on one of the Charters of Freedom encasements with a helium mass-spectrometer leak detector system. To verify that all the seals were properly set, the leak testing procedure was performed after each assembly step. (Credit: Eric Whitenton, NIST)


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© 2011 The Minerals, Metals & Materials Society



They are the unsung heroes of iconic ideas forming the bedrock of civil society. Using ink brewed from iron and extract of oak galls, they committed to parchment in a fine, flowing hand the edicts of kings and the hope of nations. The documents that have survived them are the physical embodiment of not only astonishing thought, but also of the more mundane details of law, commerce, and convention.

Those unnamed scribes and clerks from centuries ago probably had little clue that their painstaking work would be the window through which subsequent generations could seek understanding of who we were and what we might become. They would also most assuredly be amazed at the tools and technologies now deployed to keep those windows clear and open for the foreseeable future.

The most cutting edge of these techniques are currently being implemented to protect one of the four remaining originals of the 1297 Magna Carta for a new permanent exhibit slated to open March 2012 in the West Rotunda Gallery of the U.S. National Archives Building. "Working with a very significant document such as the Magna Carta creates a big responsibility to make sure everything is planned and carried out correctly down to the smallest detail," said Catherine Nicholson, deputy director of the Document Conservation Division, National Archives and Records Administration (NARA) and project manager for the Magna Carta encasement initiative. "But, the reward is the sense of pride in helping to make such an important document last as long as possible. To get to handle a document that was written more than 700 years ago is amazing."


The original Magna Carta was issued in 1215 when an assembly of aggrieved barons forced King John of England to write down and confirm with the royal seal that he and his heirs would recognize traditional liberties. Modified versions of the Magna Carta were reissued by each of King John's successors, with the 1297 iteration, confirmed by Edward I, being significant as the first Magna Carta entered into the official Statute Rolls of England, marking its transition from a brokered agreement between the king and his feudal lords to the foundation of English law.

The majority of the original Magna Carta's clauses have long since been repealed because they focused on addressing specific feudal customs and other controversies of the day. Its lasting legacy, however, has been in establishing fundamental principles of a free society—that a government leader's authority is not above the law and "no free man shall be seized or imprisoned, or stripped of his rights or possessions, or outlawed or exiled . . . except by the lawful judgment of his equals or by the law of the land." Its echoes resonate through everything from the U.S. Constitution and Bill of Rights to the Universal Declaration of Human Rights adopted by the United Nations in 1948.

The 1297 Magna Carta currently undergoing conservation treatment at NARA had languished for years in a damp English castle before its significance was recognized in the last century. The historic sheet held up remarkably well through the ages, said Nicholson, "surviving by the good fortune of being stored in a place that mostly protected it from vermin, fire, floods, and excessive handling and exposure to light." Its 2,500 words were penned in medieval Latin with ferrogallotannate, or iron gall, ink.

As was typical in 13th century England, the charter was inscribed on parchment made of animal skin soaked in a lime bath, dehaired, and then stretched on a frame to dry. While the skin was scraped to create a smooth writing surface, the parchment was tough and difficult to work with, necessitating that mistakes or modifications be scratched out with a knife. A unique aspect of this particular Magna Carta is its honey-colored wax seal suspended by a narrow strap of parchment laced through a folded flap at the bottom of the document. The wax bears the central part of the Seal of King Edward I, showing him seated on a throne.

The Perot Foundation purchased the ancient document from a British family in 1984 for $1.5 million, subsequently loaning it to the National Archives for display in 1985. The only original Magna Carta located in the United States, its new abode was a sealed metal box with an acrylic cover bolted against synthetic gasketing. The box was then filled with inert gas that was humidified and replenished every year or two to preserve the document and keep the animal skin from warping.

In 2007, the Perot Foundation terminated its loan with the National Archives and put its Magna Carta on the auction block. David Rubenstein, co-founder of the private equity firm, Carlyle Group, was concerned that it would end up in a private collection, never to be seen again by the public. Arriving with just minutes to spare at Sotheby's, New York, on the day of the auction, Rubenstein placed the winning bid of $21.3 million for the charter and then immediately announced that it would return to the National Archives on loan from him as a gift to the American people. Rubenstein is also underwriting the cost of ensuring the Magna Carta's continued longevity with state-of-the-art encasement technology.


Shortly after its last day for public viewing on March 1, 2011, the Magna Carta was transported to an undisclosed location where a team of conservators (Figure 1) began poring over every centimeter to determine its condition and develop a treatment plan. Their work, as Nicholson describes it, seems "an amazing combination of science and art." Over the next year, they will evaluate issues such as moisture sensitivity, material composition, and possible reactions to proposed conservation treatments and encasement. In terms of repair, any small holes resulting from materials degradation or the appetite of a long ago insect will be filled with meticulously shaped handmade Japanese paper toned to match the original document. While some ink has been lost to dripping water over the centuries, no attempt will be made to "rewrite history" by replacing even a single period. However, with a camera employing ultraviolet radiation, remnants of writing invisible to the naked eye will be revealed by ultraviolet fluorescence and photographed.

Nicholson said among the Magna Carta's greatest preservation challenges is its potential to expand, contract, and distort from its sensitivity to changes in moisture content. The iron gall ink is also highly susceptible to fading under light.

Since storing the Magna Carta in the dark, away from all possible environmental encroachment is not an option, Nicholson is working with a team of fabrication specialists at the National Institute of Standards and Technology (NIST) under a Memorandum of Agreement to design and construct an encasement that offers the next best thing. Nicholson said that the choice of a tightly sealed metal encasement filled with inert gas will prevent photo-oxidation of the ink, while an approach to carefully monitor and control the amount of humidity will keep the parchment from distorting. The new encasement, she noted, will necessitate changes in how the Magna Carta had been displayed in the past. "The previous display supported the document on a linen-covered window mat, assembled with pressuresensitive adhesive," explained Nicholson. "In a very tightly sealed box, the goal is to avoid organic materials such as linen or adhesives that can release volatile gasses, such as acetic acid, into the sealed atmosphere. The concentration of these gasses can grow over time inside the sealed box and cause deterioration."


The encasement solution being developed for the Magna Carta is based, in large part, on technology that NIST pioneered for the 2003 re-encasement of the U.S. Constitution and Bill of Rights and the Declaration of Independence, collectively known as the Charters of Freedom (Figure 2). Prior to that initiative, the documents had been displayed for more than 50 years in helium-filled encasements developed by the National Bureau of Standards, the predecessor agency to NIST.

"The original Charters encasements were an elegant solution to providing a protective enclosure with a low oxygen level," said Charles Tilford, retired NIST physicist and a member of the Charters project team. "They were an inexpensive adaptation of a commercial product—thermopane windows—that used a proprietary process to apply a very adherent copper coating to the perimeter of a glass sheet. This allowed the encasements to be assembled by soldering the edge of the glass to a lead strip that separated the two pieces of glass, providing a 'hard' seal that resulted in negligible intrusion of air over half a century for five of the seven encasements."

Clever and groundbreaking for its time, this particular solution still had its drawbacks, such as soldering with the documents inside the encasement. Said Tilford, "A low-temperature solder and a very skilled Libbey-Owens-Ford factory worker allowed the assembly to be done very quickly with minimal heating, but any risk of overheating is no longer acceptable." In addition, the helium that filled the encasements diffused slowly through the glass, and apart from a "primitive leak detector," according to Tilford, no instrumentation was used to monitor the conditions inside the container.

While the documents themselves faced the test of time fairly well, the encasements did not. Imaging technology adapted from the U.S. space program by NASA's Jet Propulsion Laboratory revealed that the glass had microscopically deteriorated, with minute crystals and microdroplets of liquid forming on the glass surfaces. This not only meant that the damaged glass would slowly become opaque over time, but it also indicated a build up of potentially damaging humidity inside the encasement environment.

An important lesson learned from the aging encasements was the need for flexibility. The new Charters of Freedom encasements, as well as the evolving Magna Carta encasement, can be opened and resealed to replace deteriorating parts and allow for conservation treatments on the documents. Also integral to the design is sophisticated instrumentation monitoring the slightest variation in temperature, humidity, and oxygen so that adjustments can be made before problems emerge (Figure 3). Instead of helium, humidified argon gas is now used to flood the encasements. It's a natural choice for this use, said Tilford, because "it is completely inert, very pure, inexpensive, and does not diffuse through glass."

The encasements also needed to be light, but strong, to allow for easy, safe transportation. Advanced fabrication techniques were used to create each Charters of Freedom encasement from a single block of aluminum, while titanium was chosen for the frame (Figure 4). "The selection of titanium was motivated in part by its strength and light weight, but it also had public relations appeal—titanium was the high-tech material of that time," said Tilford, noting that carbon composites might be considered today for similar reasons. Because the specifications for the Charters project dictated that the seals last for a century, a highly corrosion-resistant nickelchromium alloy was used for the seal material (Figure 5).

Specific materials and approaches for the Magna Carta encasement are still being explored, said Mark Luce, NIST director of Fabrication Technology Management Resources, noting that maintaining the inside environment through a passive system is the principle driving the design. This approach, according to Luce, will greatly reduce the staff time needed for monitoring the encasement environment, as well as the frequency of replenishing the humidified inert gas sealed inside, giving the document more consistent protection over the long term. Of crucial importance, he said, is "the type, quality, and placement of the encasement seal."

At this point in the project, NIST has proposed the use of elastomer seals, rather than the metal C-seal used for the Charters of Freedom. "Experience indicates that these elastomer seals should last at least 20 to 25 years, although the quality of the seals might eventually fail because of stiffening of the synthetic polymers," said Luce. In the event that this would happen, the encasement can be opened and the seal replaced. Luce said that the groove for the seal is being designed so that it could accept a drop-in replacement of a metal C-seal, if that seemed like the better option at that time.


The current Magna Carta encasement design on the table uses two Oring seals around its circumference. Luce said this approach will reduce the infiltration of potentially harmful oxygen, while also allowing for periodic measurement of gas leakage by testing for helium tracer gas in the space between the seals. Although Luce is building on the technology developed through the Charters of Freedom project, he is also drawing from his experiences as the project leader for the 1507 Waldseemüller map encasement.

Now on display in the U.S. Library of Congress, the Waldseemüller map (Figure 6) was the first world map known to label the New World as "America," earning it the nickname of "America's birth certificate." Sharing similar materials degradation issues with the Magna Carta and the Charters of Freedom, the Waldseemüller map also added its immense size—40 square feet—to the list of encasement challenges (Figure 7). Luce said that concerns included developing a hermetic seal that could function effectively over the large surface and designing an encasement system that could absorb atmospheric pressure changes involving the volume of so much inert gas. Weight was an issue, too, since the encasement could not exceed existing floor load limitations.

Using lightweight aluminum for the encasement's frame and base partially addressed the map's potential weight problems. Elastomer seals, like those proposed for the Magna Carta, resolved some of the map encasement's design issues, while giving rise to others. "For metal seals, such as used in the Charters encasements, periodic measurement of helium leaking into the space between the seals from the interior of the encasement can be converted to a reliable measure of the rate of oxygen permeation and a check on the continued integrity of the seal," said Luce. "For elastomer seals, the conversion from measured helium leak rate to actual oxygen leak rate depends on the material properties of the seal and is much more uncertain."

In devising a solution, Luce said that NIST employed an in situ oxygen sensor to directly measure oxygen permeation. Attached to the outside of the encasement. but pneumatically connected to the interior, the sensor has parts per million sensitivity and does not use liquids or oxygen adsorbing materials, eliminating concerns for potential destructive interactions with the map material. The system has worked so well for the Waldseemüller map that NARA has approved a similar approach to be incorporated into the Magna Carta encasement.

"Most of the materials, components, and techniques used in encasement construction and conditioning are used extensively at NIST and many of them have large-scale industrial use," said Tilford. "The encasements do represent new applications with their own set of issues (Figures 8, 9, 10). Fortunately, NIST has experts with a wide range of knowledge and experiences who are used to working on new challenges and recovering from unexpected problems."

When the Magna Carta returns to the West Rotunda in 2012, its delicate parchment will offer another story beyond the words scratched on its surface. It is one of a truly amazing journey from the poorly lit confines of a scribe's quarters, to medieval castles and meeting places, to laboratories crammed with equipment usually reserved for use in cutting edge industries. Its passage from one set of hands to another in service of its protection is a testament to how far society has come since it was first written—and symbolic proof that the will of talented and persistent people will never permit a great idea to fade away.

Lynne Robinson is a news and feature writer for TMS.