Milk tokens

We have a collection of plastic dairy tokens recently donated to the
Royal B.C. Museum and Archives.  They were collected in B.C. between
1963 and 1969.  At the time, the collector washed the tokens in soap
and water or water alone and stored them in cellulose acetate bags.
Since arriving at the archives, the tokens have been rehoused in
polyethylene Ziploc bags inside Mylar coin "flip" holders.  During
the rehousing project, it was discovered that about one third of the
collection was covered in a white bloom. There was also a
distinctive sour milk odour present when the bags of the affected
tokens were opened.  I did a Beilstein test on a sample token and
found it negative for cellulose nitrate.  Testing was done to remove
the bloom and mineral spirits was found to do the job when swabbed
on the surface.  Within 2 years however, the bloom has returned. I
am thinking that the plastic has started to deteriorate resulting in
the surface bloom. Residual milk products present have caused the
odour and may be contributing to the breakdown of the plastic. Any
thoughts?

Lisa Bengston
Conservation Services
Royal B.C. Museum
675 Belleville St.
Victoria, B.C. V8W 9W2
250-387-2108
Fax: 250-356-8197


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                  Conservation DistList Instance 22:31
                 Distributed: Friday, November 28, 2008
                       Message Id: cdl-22-31-011
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