Cleaning paving slabs

[Ian]

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

[Spike]

Add a couple of drops of washing-up liquid to a watering-can of diluted bleach, and stir it in. The idea is to avoid making it foam, you just need it to be evenly distributed throughout the bleach solution. It lowers the surface tension, enabling the bleach solution to penetrate to places where the high surface tension of water would otherwise limit the penetrating power of the solution.

When the solution dries out, the active ingredient is still there, re-dampening the treated surfaces or a shower of rain will reactivate it.

Dilute bleach, especially with added washing-up liquid, will kill black spot and brown spot invasions; it might kill white spot too but the remains seem to persist.

Unfortunately it doesn't get rid of the blackened areas.

[The Natural Philosopher]

No, it wont. Or at least it wont remove the staining.

BTDTGTTS

[fred]

Moss on tarmac drive was ou problem but sprinkling it with biological washing powder (Aldi's cheapest) wiped it out. Good for a few year

[Spike]

I get an old trigger-pack - mostly the tops are a sort of bayonet fitting and are easily replaced once removed - I flush it out then add 1 part of thick bleach to 4 parts of water and two drops of washing-up liquid; then replace the top and repeatedly invert to mix the contents.

I've used this to remove several hundred black spot (and brown spot) growths from both my and my neighbours footpaths, and there's no sign they were ever there, and they have never returned. I treated them every couple of weeks for three or four treatments.

I think this kills white spot too, but they seem never to fade away; they are best zapped while very small and this seems to stop them getting any bigger.