Storing coins

Susan White <smwhitewhite [at] aim__com> writes

>Does anyone know how to tell if a particular plastic is likely to
>outgas acidic components?  I have a museum client who has been
>housing Greek and Roman bronze coins in "Archival" plastic sleeves,
>similar to photographic slide sleeves; however, the coins are
>starting to bloom with bronze disease and I'm suspicious that the
>plastic may not actually be suitable for holding bronze coins and
>outgassing corrosive reagents. I tried to test the plastic using a
>pH pen designed for testing paper, but the results were ambiguous.

It's possible that the sleeves are polyvinyl chloride (PVC), in
which case the Beilstein test is a simple way to determine presence
of chlorine in the plastic and by inference identify it as PVC. For
the test method see:

    CCI Note 17/1:
    Williams, R.S. 1993.
    "The Beilstein Test: Screening Organic and Polymeric Materials
    for the Presence of Chlorine"

You probably should make sure your client has not used chlorine,
ammonia, other cleaners, or paints in the room where the coins are
stored. Also, if the plastic pages are kept in a binder, make sure
that it is not PVC. They might want to consider purchasing Corrosion
Intercept sleeves designed for coins, which will trap any pollutants
that can cause corrosion.

Laura Wahl
Library Conservator
Hagley Museum and Library
PO Box 3630
Wilmington, DE 19807
302-658-2400 ext. 236
Fax: 302-658-3267


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                  Conservation DistList Instance 23:43
                   Distributed: Tuesday, May 4, 2010
                       Message Id: cdl-23-43-004
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