Black silver

I have recently been working on disaster recovery for the object
collection of an archives that had a smoke infiltration in a
storeroom.  All of the silver objects (probably all 20th century)
including  things from Japan, India, Israel, Chile, and the U.S. are
stone-cold black.  And the black layers are almost entirely immune
to regular silver polish, even after I clean them with detergent to
get any greasy smoke off.  If I keep scrubbing with Noxon, after a
long time I break through the black, but it's incredibly slow--not
because the layers are thick but because very little comes off at a
time.  What I mostly get from a lot of polishing is a nice shine on
the black layer.

I tested with solvents including di-methyl formamide to make sure
there were no coatings, and nothing came off.  I can't think of any
scenario that might result in the same wacky thing happening to a
group of dissimilar silver pieces unless someone coated them with
some awful commercial product, but even then I can't imagine what.
I don't think that the smoke episode was accompanied by high
temperatures, although, again, I can't imagine that that would
account for what I have.

Any suggestions would be greatly welcome.

Barbara Appelbaum
Appelbaum and Himmelstein
444 Central Park West
New York, NY  10025
212-666-4630


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                  Conservation DistList Instance 22:36
                 Distributed: Monday, December 15, 2008
                       Message Id: cdl-22-36-017
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