Coatings on ivory

Is anyone doing research on ivory, particularly coatings applied to
ivory?  We have a medieval French diptych in our collection with a
discolored brown coating, possibly brush-applied, and covering
undercut areas as well as those of high relief.  The coating appears
to be well-absorbed into the ivory substrate.

A brief trip around neighboring museums reveals other medieval
ivories with similarly darkened surfaces, due to possible coating. A
sample examined with FT-IR proved negative for oil, and indicated a
small amount of protein, which may be from the ivory itself, or may
indicate a hide glue component to the coating.

Our main question is whether the coating is original to the piece
(artist applied) or part of a later restoration (either to enhance
gloss or seal the surface).  If anyone knows of the history of ivory
preparation and restoration, or can refer me to an expert, I'd
appreciate it.

Melissa R. Katz
Davis Museum, Wellesley College
Wellesley, Massachusetts 02481
781-283-2065
Fax: 283-2064

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                  Conservation DistList Instance 13:21
               Distributed: Thursday, September 23, 1999
                       Message Id: cdl-13-21-014
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