








Removing very stubborn black lichen from sandstone
Hi,
I’m trying to remove some very stubborn black lichen from an Indian sandstone patio. There are 3 stones (1 in particular - The curved one) where I just cannot get the stuff off. So far I’ve tried… Pressure washing alone. A water based biocide then pressure washing. Sodium hypochlorite and stiff brush. This helped get some light stuff off a few of the lesser affected stones but these 3 remain stubborn.
With the hypochlorite I wet the surface first, applied solution neat, scrubbed with stiff brush. Repeated application and scrubbing every 15 minutes for about an hour. This lightened it slightly on 2 of the stones and the 3rd ever so slightly (maybe).
Various AI’s can’t agree on the best way forward.
Does anyone have a recommendation?
I’d like to get the whole lot sealed before winter kicks in and want to clean this off first if possible.
Thanks.