Corrosion

Two commemorative medals described merely as 'gold-toned' recently
entered our collection. They have a matte gold surface and are quite
heavy.  Both show significant spots of corrosion which is reddish at
the outset, deepening to a dense blue-black sheen where farther
gone. The medals are currently stored in cloth-covered presentation
cases, the lids of which are padded (probably with a synthetic
batting) and covered with a satin-type fabric.  These are stamped in
gold with a decorative seal.  The medals themselves fit into plastic
forms with a synthetic velvet-like covering fused onto the plastic.
The back of one medal has remained completely corrosion-free on one
side (the side resting in the form). Both sides of the other medal
are exhibiting corrosion.  Most likely it was turned at some point
in its form.

The most pressing question for the moment is what role, if any,  the
presentation case lids are playing in this corrosion.  Or, is the
problem inherent in the composition of the medals themselves?  Any
advice would be appreciated.

Kim Koons, Museum Technician
Office of Presidential Libraries
National Archives and Records Administration
Washington, DC

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                  Conservation DistList Instance 12:29
                Distributed: Tuesday, September 22, 1998
                       Message Id: cdl-12-29-019
                                  ***