Chris Thornton wrote:
>
> -"brass" or more specifically Roman brass (containing >30% Zn), to which
> Peter was referring, begins around the Christian error.
This certainly is a Christian error!!! Craddock and many others have
done hundreds of analyses of Roman and Islamic brasses; you can find
most of the references in papers in Paul Craddock (ed) 2000 Years of
Zinc and Brass, British Museum Publication no. 50, 1990, and see also
more recent papers by Justine Bayley and Thilo Rehren on Roman brass in
JHMS and JAS. Essentially all Roman brass, and most Islamic brass, has
less than 28% zinc, which is (according to Craddock) the upper limit
attainable by cementation - the reaction of calamine (ZnO) with copper
and charcoal in a sealed crucible. Brasses with >28% Zn are made by
adding metallic zinc to copper, which explains their rarity before the
invention in the Indian subcontinent of methods to distill and condense
metallic zinc - for which see the Craddock book - in the ??early second
millennium AD. Thr Romans did not know how to produce zinc metal
consistently, and it was a latecomer to the western Islamic world. I
have analyzed a lot of Islamic brass from West Africa, and there is not
a single piece in stratified context that has >30% zinc. In those areas
in direct contact with India, such as the Arabian Gulf, it is however
quite common after 1300 AD.
Dave Killick
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