Use caution when cleaning a gravestone; avoid the use of household soaps, acids and other cleaners, especially bleach, that cause yellow staining of marble and may cause further damage to the marker. Only attempt cleaning if there is access to running potable water.
For basic cleaning, remove any plant growth from the stone carefully, cutting away growth rather than pulling it off. Wet the stone with the water and rinse away any dust from the surface of the stone. Begin cleaning at the bottom of the stone and work toward the top to prevent streaks and stains. Use a soft bristle brush to scrub gently in a circular motion. Keep the brush wet by dipping it into a bucket of clean water or running water from the hose over the bristles.
Avoid the use of a dry or wire brush when cleaning a gravestone, as they can cause erosion of the stone and increase the potential for damage due to weathering. If you need a tool to remove growth from the stone, choose a wooden craft stick or bamboo skewer softer than the stone. If the stone requires a cleaning product, choose an architectural antimicrobial formulated for use on stone. Once you finish cleaning the stone, rinse it again with water to remove any loose materials.