Granite is a popular material choice when it comes to tombstones, as it is an elegant stone that is also durable enough to withstand years of weathering and exposure to the outdoor elements. Since the tombstone is outdoors, it will require cleaning every few years, as you see fit, when residue and film leave the tombstone looking unclean.
Fill one spray bottle with clean water, and fill another spray bottle with 2 cups water and 1 tbsp of a pH-neutral soap such as dish detergent.
Spray the soapy solution onto the tombstone, and scrub with a soft brush.
Scrub engravings and crevices with an old toothbrush.
Spray the clear water onto the tombstone, and wipe clean with a dry cleaning cloth. Wipe in small circular buffing motions. This will remove soap residue and also polish the granite.