Salt on glass

There is another situation, which may be similar to the salt
deposition that was observed in packages at the British Museum.
Sodium chloride has been found on the inside surface of the glass in
frames used on old prints. It formed a "ghost" pattern on the
surface of the glass that loosely followed the pattern of the print.
It has been speculate that the sodium may have come, in this case,
from the glass, but the source of the chlorine is unknown.

When such packages are sealed, strips of plastic/aluminum sealing
foil (Marvelseal 360, 470, Mitsubishi PE/AL/PET/PE) can be used in
the role that Ms. Leach outlines for MicroChamber paper in creating
a barrier between the tape volatiles and the interior of the
package.

Hugh Phibbs
Coordinator of Preservation
National Gallery of Art
Washington, DC 20565


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                  Conservation DistList Instance 17:10
                   Distributed: Monday, July 7, 2003
                       Message Id: cdl-17-10-007
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