Ben wrote in message ...
Bill F wrote:
Does anyone have a sucessful method to remove lichen from concrete
textured paving slabs. The lichen forms small black circular patches
1-3cm in diameter and looks unsightly. I have tried various chemicals,
acids and detergents without success. Powerhosing works but it damages
the surface of the slabs leaving rough, eroded areas.
Best wishes
Bill F

I used to have black spots on my concrete paving slabs (although I
assumed it was mould, not lichen) and nothing would shift them. Like
you, I tried all kinds of chemicals, acids and detergents, and resorted
to abrasive techniques (wire brush - I don't have a pressure washer)
which just ended up damaging the concrete. In the end, the solution was
frustratingly similar to the very first thing I'd tried. Repeated
application of neat *thin* bleach - not thick bleach! The thin stuff
soaks into the concrete and kills the roots (or whatever it is that
mould has), or at least that's my explanation. The thick stuff just sits
on the surface and has no effect at all.

Ben
Thanks for your suggestion - I tried thin bleach today and it seems
to work just like you said, one or two applications get most of it
off. I've ordered 50 litres more from our local Tesco, at 28p for 2
litres it seems a bargain. If they sold it as patio cleaner they
could probably make a killing.

Thanks again for the advice
Best wishes
Bill