"The Natural Philosopher" wrote in message
...
marvelus wrote:
On 07 Oct 2006 23:37:19 GMT, (Andrew
Gabriel) wrote:

In article ,
marvelus writes:
On Fri, 6 Oct 2006 13:42:35 +0100, "Andrew Mawson"
wrote:

However if you can get someone to install a thin taut bare
copper wire
either side of the ridge, rain (which is slightly acidic) will
form
copper salts which washing down the roof will kill the lichen
This is a myth.
Nope. There was a brilliant example next door to my grand
parents.
Their bare phone wires passed over the roof of next door
bungalow.
There was a very straight line across the roof some ~5' under the
phone wires were any drips would land. From that line all the way
down the the gutter, the roof was completely clear of moss and
lichen.
Above that line, it was covered in both. That was the first time
I
noticed the effect, long before I ever read or heard about it
anywhere else.


There is no evidence to support this nonsence. If you have any
other
than some unsuported anecdote please share it. Otherwise there is
no
way some insignificant dilutions of copper salts, which would be
washed away by the same rain thats supposed to be spreading them,
could act as a weed killer. The same sort of people who believe in
this probably also believe in homeopathy. Maybe your auntys
neigbours
friends mother has a rabits foot tied to the tv ariel to kill the
moss.

You can see copper staining near to any copper metal thats exposed
to
sun air and rain.

You can see copper plated rooves that never seem to have lichen on
them.

Copper has long been known to inhibit shellfish and seaweed
encrustations.

Not conclusive proof of this, but it does indeed show that copper
salts
do NOT wash away. And that copper itself, and salts thereof probably
are
efficient anti-(some kinds of life at least) agents.

I wouldn't be too quiock to condemn.

Actually, since I have a lichen problem I';ll throw some copper on
it
and see what happens.






Some antifouling for boats is copper based to inhibit growths - see:

http://www.coppercoat.com/howitworks.htm

AWEM