Jethro_uk wrote:

On Tue, 24 Dec 2019 12:20:42 +0000, Brian Reay wrote:

On 24/12/2019 11:48, Dan S. MacAbre wrote:
Brian Reay wrote:
On 24/12/2019 10:27, Dan S. MacAbre wrote:
Mr Pounder Esquire wrote:
Bungalow, back end south facing. I was unhappily on the roof about 5
years ago scrapping and brushing the moss off. The tiles are very
rough and are like steel.
I'd read that stringing a length of copper wire over the ridge kills
moss,
so I did it. The moss returned on the back end of the roof, never
mind and ******** to it, I'm not going up there again. Since Autumn
chunks of moss have been falling down almost every day. Maybe the
copper wire takes time to work?


Ferrous Sulphate is my favourite for moss. It is dead (but black and
unsightly) within a few hours. But you'd have to somehow spray it
all over the roof.


Do you know if it is toxic when it gets into the soak away etc? I'm
not suggesting it is- I collect water from part of our roof to water
the garden etc.

I believe it is used to treat anaemia, so certainly not toxic in small
doses :-) If watering the garden with it, note that if sufficiently
concentrated, it will tend to noticeably iron stain light paving stones
and similar things.

As an aside, I had heard Copper Sulphate also worked and had assumed the
copper wire trick was a variation on that- possibly due to a reaction
with sulphides in rain but hadn't looked into further.

Is there as much sulphur in the air as there used to be ? Haven't heard
about acid rain for a while ...
I expect it is the copper ions in solution that are important, not the
sulphate. So whater the corrosion process, perhaps involving water,
oxygen and CO2, some copper will diffuse about the tiles when damp.


--

Roger Hayter