(The following is an article in the September/October 2016 issue of the Library of Congress Magazine, LCM. The article was written by Fenella France, chief of the Library’s Preservation, Research and Testing Division.)
Technological advancements have made it possible for the Library to put several rare maps on long-term display.
Preserving and making the Library’s vast collection accessible to researchers is a challenge. Even more challenging is putting rare and unique items on display. Lighting, temperature and even air itself pose a threat.
The Library, in collaboration with National Institute of Standards and Technology (NIST), has designed, constructed and installed anoxic (oxygen-free), hermetically sealed encasements to mitigate the potentially damaging effects of long-term display.
Oxygen promotes the deterioration of materials such as paper, parchment, and organic-based media including inks and other colorants. This deterioration is often visible as yellowing, embrittlement and color-fading.
Anoxic encasements are created by displacing oxygen with an inert gas, such as nitrogen or argon. A good seal that can maintain interior case conditions requires advanced case construction, materials and design.
In addition to allowing oxygen-free display, the encasements have to meet preservation needs for long-term display of historic materials; allow monitoring of the maps by measuring environmental changes; integrate with the Library’s electronic and security infrastructure monitoring and be movable.
The Library first began using the special encasement in 2007 to display Martin Waldseemüller’s 1507 world map— the earliest known map to name the land mass of “America.”
More recently, the Library worked with NIST in 2013 to design, construct and install another anoxic encasement to display Abel Buell’s 1784 map— the first map of the newly independent United States that was compiled, printed and published in America by an American.
One challenge in the design of the Buell map encasement was to replace an oxygen sensor used for the previous encasement monitoring that was no longer commercially available. A prototype of the sensor was built, calibrated and tested, and is currently in use for the monitoring of the interior conditions of the Buell case.
The encasement, tooled from a single block of aluminum and covered with hurricane- proof glass, allows tight control of the map’s environment, reducing its potential degradation by oxygen and moisture. Performance testing of cases and sensors is an ongoing program in the Library’s Preservation Research and Testing Division.
You can read the complete issue of the September/October 2016 LCM here