Silver foil for Oddy tests

Laura Gorman asked for sources for silver, 99.5% pure with a
thickness of .1mm.

Silver foil, .127mm thick, 99.9% pure, is available through Alfa
Aesar 1-800-343-0660). The 1997-98 catalog lists the price as $23.40
for a 50mm x 50mm square.

Perhaps someone from the British Museum would care to comment on the
relevance of thickness of metals used in conducting Oddy tests. As I
understand it, evaluation of oddy tests is based on the observation
of corrosion on the *surface* of metal coupons. Substituting a
coupon of a different thickness would only marginally change the
surface area of the coupon, and would therefore have little effect
on test results.

While I agree that standardization of the Oddy test procedures is a
laudable effort, perhaps a little flexibility could be introduced in
coupon thickness and purity.  Will the use of a 99.9% pure metal or
a 99.4% pure metal produce results that deviate appreciably from
those produced with a 99.5% coupon.

The ubiquity and the beauty of the Oddy test are largely  functions
of its simplicity.  It's quick (okay, not quick) and dirty.  It's
low-tech. It's not rocket science.

Will Jeffers
Collections Care Specialist
Museum of Fine Arts, Boston

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                  Conservation DistList Instance 12:34
                 Distributed: Saturday, October 3, 1998
                       Message Id: cdl-12-34-004
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