Now we have to a little careful here!! on many marble gravestone the lettering is sitting flush with the surface of the stone, looking like it has been painted on, well it isn't paint and hasn't been painted at all. The lettering is incised and then lead is hammered into the incised lettering, the lead being a very dark grey. To clean this lettering and the gravestone, I would recommend the use of 220 grit wet and dry abrasive paper wrapped around a piece of wood along with a bucket of water to keep it really wet. Do not attempt to paint the lettering, do not use pumice stone on this type of lettering.