How do you clean black slate on a fireplace hearth? There are white water stains which I cannot remove.
Using a pot scrubber pad and T.S.P. mix 2 tablespoon into 1 quart hot water. Apply to slate in a puddle. Wear rubber gloves and scrub with scotch brite pad and allow to sit for 5 – 10 minutes scrub again and rinse. Allow to dry. Apply 2 coats slate gloss available at Lumberworld or Slegg Lumber.