:) Hi all, Anybody got any ideas what I should clean Portland stone with ??? It has lichens of all colours & types growing on three sides, which are lovely & I want to keep of course, but I have this green algae type stuff on the other side where plants have been up close to it :( I would like to keep this side of the stone clean. I have been told not to use bleach or the like as it is quite well fossilised & that would damage it. :( Have used soap & water so far but it doesn't really get it off. ??? ::) So any help appreciated, thanks :)