Keywords: ChartersOfFreedom 030.jpg Tubes sealed in holes drilled through the lead strip in diagonally opposite corners of the Declaration of Independence enclosure served as inlet and outlet ports for the helium The ports permitted the complete replacement of the air atmosphere surrounding the document with specially humidified heliu Pictured is Louis Gilles of the Libbey-Owens-Ford Glass Company National Institute of Standards and Technology National Institute of Standards and Technology The images in the ChartersOf Freedom Photographic Collection are in the public domain and are not subject to copyright in the United States However please pay special attention to the individual works to make sure there are no copyright restrictions indicated Individual works may require securing other permissions from the original copyright holder Use of the images from NIST Digital Collections is not restricted but a statement of attribution is required Please use the following attribution statement National Institute of Standards and Technology Digital Collections Gaithersburg MD 20899 PD-USGov National Bureau of Standards National Institute of Standards and Technology Libbey-Owens-Ford Company United States Declaration of Independence |