This question was submitted from Bob D.
“How do I remove black marks, probably mould, from a polished granite tombstone? How do I clean up a tombstone generally?”
Usually, you don’t want to use harsh chemicals on stone like granite or marble.
Try these techniques :
If the problem is mildew, a mild solution of 1 part bleach and 4 parts water will kill the mildew. I am not a stone expert and am unsure if granite will have a negative reaction to bleach – I expect it would not, but it would be best to test a small area first.
Otherwise, use a neutral detergent (dish soap and water) or any other neutral cleaner (Ph of 7; this would exclude ammonia or acid based chemicals).
You can use superfine stainless steel (#0000) if the stains are stubborn, or a plastic scrubber.
If you are going out to a cemetery bring a large Tupperware container with your soap solution mix with hot water – so if it takes sometime to arrive it will at least be warm.
If possible bring a container with clean water for rinsing.