In message ,
"Mary Fisher" wrote:


"Martin Angove" wrote in message
...
Piece of T&E behind a hardboard facing on a damp wall of an old
stone-built ex-barn,

[...]

So for the chemists here (I'm sure there must be some) what is happening
to the Copper? What is the green stuff?

I've been reading this thread carefully and while I can't comment on the
technical electrical stuff I used to be a chemist so, because I haven't seen
any correct response to this specific question I'll tell you.

It's almost certainly copper carbonate (cupric carbonate-hydoxide), a pale
green powder as opposed to a crystalline salt. Copper in the presence of
atmospheric moisture and carbon dioxide produces copper carbonate. Cupric
oxide is black by the way, cuprous oxide is red.

This green stuff seems very similar to the usual sort of thing which
happens to Copper if left outside / in the damp,

That's because it's the same stuff.


Brilliant, thanks for this. I'm happy with what I have done electrically
(you should have seen the circuit's readings before I started!) I was
just trying to satiate my curiosity about the physical process involved.
If I may ask a cheeky follow-on question...

....the screw terminals in the socket are... ummm... brass I should
think. Some sockets seem to be all brass, or maybe brass and
copper, others have brass terminals riveted (in the case of the Earth
which can be seen) onto steel.

Damp (plus unknown contaminants) plus copper plus brass plus pressure
equals ?

Yes, I have seen very blackened exposed copper in this combination, but
usually cutting back an inch or so reveals something approaching shiny
:-)

Hwyl!

M.

--
Martin Angove: http://www.tridwr.demon.co.uk/
Two free issues: http://www.livtech.co.uk/ Living With Technology
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