Tin pest

Thanks to the people who have sent in possible/probable examples of
tin pest. I don't want to prolong this thread unduly, but these are
my thoughts:

I am prepared to believe in the Russian tin ingots and the Russian
army buttons, but I don't believe in Captain Scott's kerosene cans
or the Kas shipwreck tin vessels.  I can believe that the ingots and
the buttons were made of pure tin which was exposed to very low
temperatures for long enough for the transformation to grey tin to
occur.  While the kerosene can were exposed to low temperatures I
would have expected the solder to be a lead-tin alloy, which would
not be expected to transform.  I find it very difficult to believe
in the Kas vessels, because although the temperature at the bottom
of the sea is no doubt below 13.2 degrees it is not that low.

The point about all these cases is that there is no unambiguous
identification of grey tin by X-ray diffraction, for example.  I
would be interested to hear how grey tin was identified on the Kas
artefacts.

Barry Knight
English Heritage
London

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                  Conservation DistList Instance 12:40
                 Distributed: Monday, November 2, 1998
                       Message Id: cdl-12-40-006
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