Posted: Thu Sep 06, 2018 6:05 pm
I laid a driveway a few years ago with tumbled Yorkshire sandstone setts. It look fantastic. I sealed it with a good product. After a couple of years a few started to turn black which got worse. Bleach and power was would not remove it. I then stripped the sealer off one of the affected stones and then tried bleach again with no success. I assumed the black was a mould underneath the sealer but is not
ANY IDEAS??
ANY IDEAS??