On 13/03/2016 16:36, Martin Spaink wrote:

> Right Peter, the so-called 'verdigris'

As I understand it, 'bronze disease' is not quite the same thing as 
verdigris. Verdigris is copper carbonate which forms a protective film 
on the object, preventing further corrosion; 'bronze disease' is copper 
chloride, which is corrosive and which can burn a hole through the 
object if it goes unchecked. It requires the presence of chlorine ions 
to form. Probably some outdoor verdigris - for example in seaside towns 
- is actually a mixture of carbonate and chloride.

As I understand it, 'bronze disease' is is more of a problem with brass 
instruments, which naturally have to be handled all the time and pick up 
chlorine in the salt from players' perspiration. But I think I have seen 
it on brass clavichord strings.


-- 
Peter Bavington
Clavichord Maker
291 Sprowston Mews
LONDON
E7 9AE
www.peter-bavington.co.uk

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