Black silver

Barbara Appelbaum <aandh [at] pop__mindspring__com> writes

>I have recently been working on disaster recovery for the object
>collection of an archives that had a smoke infiltration ...

Most probably, if the blackening has developed during the smoke
episode, you could be facing an halogen contamination on your silver
collection.

If this is the case, any silver polish is to be banned as you are
just rubbing the surface, so loosing precious material, but never
this aggressive treatment will reach the thickness you require.

Temperature was certainly not a problem and is easy to see that the
face of the artefacts lying against a wall must remain cooler than
the exposed side and therefore should had developed different area
according to exposure effect.

The favour of halogen stand for the very static molecule behaviour
and it follow preferentially an electrostatic route rather than any
other factors such as airflow. We personally had experienced this in
January this year with 30% Cl in our laboratory!

Not willing to send recipes without having study slightly the true
nature of your problem, but certainly a treatment toward a surface
reduction reaction must be investigated.

If you need more help, do not hesitate to contact us.

David Cottier-Angeli
CottierMetal
5C Route des Jeunes
CH-1227 Geneva
+41 22 300 19 55
Moble: +41 79 319 319 0


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                  Conservation DistList Instance 22:37
                 Distributed: Friday, December 19, 2008
                       Message Id: cdl-22-37-002
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