Archival Plastics & Ephemera Preservation

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www.loc.gov/preserv/newmylar.html

Update on Acceptance of Polyester Film Products for Use in Encapsulation of Paper Artifacts

Revised October 22, 2004)

Over the past several months, we have tested several biaxially oriented polyethylene terephthalate (PET) polyester films and found them to be satisfactory for use in encapsulation of paper artifacts. The acceptable films are:

* Melinex® film types 455, 456, 515, 516, KL and KM made by DuPont Teijin Films, Hopewell, VA 23860.
* Hostaphan® 43SM film, made by Mitsubishi Polyester Film, LLC, of Greer, SC 29652.
* KC Inc.'s films SH71S®, SKC SH72S® and SKC SH18S®. These films are available from Interfilm Holdings Inc., 223 Pine Road, Easley, SC 29642.
* Tairlin CH28® film, manufactured by Nan Ya Plastics Corporation, Taipei, Taiwan, and available from Granwell Products, Inc., 185 Fairfield Avenue, West Caldwell, NJ 07039.

To the best of our knowledge, all of the tested films, with the exception of Melinex type KL and type KM films, are coated for slip on one or both sides for ease of handling. The two uncoated films are available in very small thicknesses, 92 gauge for Melinex® type KL and 48-200 gauge for type KM, which conservators may find limiting for many applications (100 gauge equals approximately 1 mil or one thousandth of an inch). While we would generally prefer uncoated stock to eliminate any chance of an unforeseen interaction with the artifacts being encapsulated, we do realize that most processors find slip coating to be essential for ease of handling. Moreover, most such coatings are highly stable.

While we have found the films mentioned above to be generally acceptable for use in paper conservation, the ultimate test for acceptability of any polyester film must be the ease and consistency with which these films can be sealed or joined with the equipment that is available to the individual user.

We are pleased to share information about product testing with the preservation community, with the understanding that information concerning favorable test results in no way implies product endorsement. Vendors are strictly prohibited by law from implying or claiming that the Library of Congress endorses any specific product, service, or material.

An essential cautionary note: Research in our laboratories has clearly shown that, over the long-term, encapsulation of papers without an alkaline reserve is likely to hasten their degradation. The real and immediate gain in protecting fragile paper from physical handling needs to be weighed against the equally real risk of faster aging. However, clear and practical solutions are available to conservators to avoid this balancing act. With the many options available for deacidification today, most papers can be deacidified before encapsulation. Where this option is not available or desirable for whatever reason, a sheet of alkaline paper inserted within the polyester envelope will also overcome the effects of trapped acids formed in the aging of paper, and actually help extend the life of the encapsulated artifact.

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I decided to post this here rather than starting a new thread...

Charter Service: Encasing the Magna Carta



ScienceDaily (Feb. 8, 2012) — You often hear about the Framers of the Constitution, but not so much the framers of the Magna Carta. They work for the National Institute of Standards and Technology (NIST).

Not the authors, of course; they've been dead 700 years. But a NIST engineering team, at the behest of the National Archives, designed and built a state-of-the-art encasement and transport cart to protect the Archive's prized copy of the 1297 Magna Carta. Their work -- and the freshly conserved Magna Carta -- were on display Feb. 2, 2012, at a special "behind-the-scenes" showing at the National Archives Conservation Lab. The enclosure is designed to visually enhance the parchment document while maintaining the interior environment so it does not degrade the document, which is the underpinning to Western Civilization and U.S. law.

The encasement is basically a controlled environment, explained NIST Project Engineer Jay Brandenburg, who regularly does similar tasks to isolate sensitive lab equipment.

The first Magna Carta was signed in 1215 by King John of England. He was forced by an assembly of barons to put in writing, for the first time, the traditional rights and liberties of the country's free persons. After another confrontation with barons, Edward I not only reissued the Magna Carta in 1297, but for the first time, it was entered into the official Statute Rolls of England and became the foundation of English law.

The owner of this copy of the Magna Carta, David M. Rubinstein, loaned the document to the National Archives and paid for its restoration and encasement.

While the Archives refurbished the parchment, NIST engineers and crafts people built a platform to hold the Magna Carta, the large encasement it sits in and a heavy-duty cart.

NIST worked from a three-dimensional laser scan of the document to support it on the platform and to create a nest to hold the original wax seal with Edward I's likeness, which is attached to the Magna Carta by a frail parchment ribbon.

The platform was created from a single 6-inch thick block of aluminum to minimize the number of joints or spots that could cause leaks in the encasement, explained Brandenburg. About 90 percent of the block was cut away with a computer-controlled milling machine based on the three-dimensional image to create the perfect fit.

The end result is an enclosure about 41 inches wide by 28 inches long and 6 inches deep. It weighs 225 pounds. The encasement cover is made of a special laminated glass with antireflective coatings to ensure maximum visibility of the document while protecting it. The encasement is sealed with close-fitting bolts that hold the frame against double O-rings that create the encasement seal. The case was filled with argon gas and will be monitored to avoid as much oxidation damage as possible.

The enclosure will likely never be seen in its entirety again. By mid-February it will be placed inside the new interactive display in the West Rotunda Gallery of the U.S. National Archives Building in Washington, D.C. There, alongside three other documents for which NIST built similar enclosures -- the Declaration of Independence, the Constitution and the Bill of Rights -- it will be on display for the 1 million visitors that pass through the Archives each year.

feeds.sciencedaily.com/~r/sciencedaily/~3/xQ4pBsFdrzg/120208132842.htm

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