Rolled copper bead

Linda J. Bartol <104207.3716<-a t->compuserve< . >com> writes

>I am looking for information on the best conservation method for a
>rolled copper bead from a Contact Period Native American shell
>midden.

Even if you know for a fact that there are cuprous chlorides in the
corrosion crust of the bead, nothing needs to be done other than to
replace the soil in the container with dried silica gel (as a
desiccant).  I  would also put a humidity indicator strip (available
from archival supply houses) or cigar humidor dial hygrometer
(available from your local tobacconist) inside the container so you
can monitor the RH.  It should be below 35% in order to stabilize
the corrosion.

I would suggest using a glass container with a tight lid and then
wrapping the outside of the lid where it meets the glass with
aluminum tape.

If the surface corrosion on the bead needs to be cleaned in order to
see surface details or have it "read" more clearly for display, then
there are methods to do that.  They require knowledge of the
chemicals used and a fair amount of  experience in the actual
application of such treatments.  I would strongly advise against
applying cleaning 'recipes' that you might get as a response to your
request on the Internet.  In the case of archaeological objects, you
can do much more damage to the object and its inherent information
by performing a bad treatment or by performing a good treatment
badly than you can by performing no treatment at all.  Corrosion and
soil can provide much information when analyzed properly.   If you
become convinced that you must clean the surface, then I would
strongly suggest that an experienced professional archaeological
conservator be contacted for specific advice. Sincerely,

Paul S. Storch
Objects Conservator
John and Martha Daniels Objects Conservation Laboratory (JMD-OCL)
B-109.1, Minnesota History Center
345 Kellogg Blvd West
St. Paul, MN  55102-1906
612-297-5774
Fax: 612-297-2967

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                  Conservation DistList Instance 11:41
                 Distributed: Friday, October 31, 1997
                       Message Id: cdl-11-41-007
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