On 07/11/2020 14:54, The Natural Philosopher wrote:
On 07/11/2020 14:17, F wrote:
On 07/11/2020 09:37, The Natural Philosopher wrote:
On 06/11/2020 20:59, F wrote:
We've got a patio made up of light coloured concrete paving slabs
with a slightly rough texture. I've used a Karcher power washer to
remove the compost that the resident gardener has managed to tread
into them but there's a green stain (algae?) that's pretty resistant
to removal.

Anyone got any suggestions on what might shift it?

Green goes with bleach and heavy power washing. Its the black ones that
are impossible to shift.

We have black too. Forgot to mention that.

If BAC50 shifts it, please let us know.
I've tried everything


have you tried thin bleach as demonstrated on various Youtube videos
although many example swimming pool chlorine.

I have had a huge amount of black and green lichen on concrte pavers and
simply brushed on the bleach over a slightly dampened surface on a sunny
day and kept it damp for the rest of the day. If no kids or pets around
I left it and 98% has gone in one or two sessions. Exception is the
crumbly edges which are a bugger.

Oddly, as mentioned in one video, it seems to go on having an effect for
a while afterwards. Good luck