Copper beads

Carrie Duran <carried [at] cityofgastonia__com> writes

>We have some copper beads from an archaeological site in Gaston
>County, NC.  We would like to do some specialized analysis on them,
>but they are too oxidized to get accurate readings.  They appear to
>be almost pure copper because there are no alloys to suggest
>European copper. ...

Basically, when it comes to archaeological metals, or any metals at
all, I would try to keep them as far away from water as possible!
The message wasn't clear about what it is that needs to be cleaned
off the copper beads in question, but if it is earth matrix it is
usually possible to work carefully by dripping a little IMS
(industrial methylated spirits) on the accumulations of earth and
then carefully and gradually removing them with dental tools. The
same can be done to excavate around items inside a block of earth to
get them out in a safe way, consolidating before lifting if
necessary. IMS and acetone are both useful in loosening earth
particles. The same goes for the "unidentified object" mentioned in
the posting.

Often IMS can also be used, in very small amounts on cotton swabs
under magnification, to clean metal surfaces directly. However, if
the beads are heavily oxidised this suggests a weak surface - which
in turn means that getting a metals conservator to do the job might
be recommendable: a conservator will be able to determine what
actually needs to be removed and how far, in addition to selecting
appropriate materials.

Gali Beiner
Conservator
Pitt Rivers Museum, Oxford


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                  Conservation DistList Instance 19:3
                  Distributed: Thursday, June 23, 2005
                        Message Id: cdl-19-3-009
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