Old cemeteries with stone grave markers can be beautiful places. The ornate marble and granite gravestones look like carved sculptures. These works of art have survived many years exposed to all types of weather. Many appear stained and dirty; some have algae or lichen growth. Cleaning a gravestone is a delicate, time consuming process. By using gentleness and patience, a gravestone can be cleaned.
Practice cleaning before going to the cemetery. Use a rock or old marble or granite tile.
Evaluate the gravestone at the cemetery. Take a "before" picture of the gravestone. Test clean a small area of the stone in an inconspicuous place. If the test area does not respond well to cleaning, do not continue. If there is any doubt the gravestone can be cleaned, do not attempt to without contacting knowledgeable experts, such as the Association for Gravestone Studies.
Pre-wet the stone with water, covering it completely. Use clear water in a spray bottle or a garden hose with a gentle spray. Pre-wetting prevents the cleaning solution from penetrating into the stone. Keep the stone wet at all times during the cleaning process.
Brush gently with a soft brush. Start at the bottom of the stones and work toward the top. Working in this direction will prevent streaks. Be especially careful when brushing around inscriptions.
Wet the stone with a non-ionic pH neutral cleaning solution. This type of cleaner is found at photographic supply or conservator supply houses. It is safe to use on marble, limestone and other porous stone material. Mix 1 ounce of cleaner into 5 gallons of water. Gently brush again with soft brush. Rinse often to prevent the cleaning solution from drying on the stone.
Clean crevices and carving details with a soft toothbrush. Rub gently.
Rinse the entire gravestone with clear water. Make sure all solution is rinsed off.
For lichen growth on gravestones, use 1 part ammonia to 4 parts water. Cover the pre-wetted area with the ammonia solution and scrub gently. Rinse thoroughly with plain water. For black algae growth use calcium hypochlorite, available at swimming pool supply stores. Be certain that it is calcium hypochlorite; it is often confused with other pool chemicals. Mix 1 lb. of calcium hypochlorite with 4 gallons of water. Use this solution only for the algae areas. Scrub gently with a brush and rinse thoroughly with water. Cemeteries are many times in remote areas. Be prepared for a variety of circumstances. Take plenty of drinking water, sun screen and waterless hand sanitizing lotion. Wear eye goggles, gloves, boots, a long sleeved shirt and long pants. Include insect repellent, bee and wasp spray, a snakebite kit, poison ivy and sumac lotion, and a first aid kit. A cell phone is highly recommended.
Never use bleach when cleaning a gravestone. Never use a metal or wire scrubber or steel wool pads to clean gravestones. Never use a power washer to spray the gravestone. Never mix chemical cleaners together. They may emit toxic fumes. Never clean a gravestone more frequently than every 18 months. Never use commercial cleaners containing soap or scents. They may leave a residue which will damage the stone. Always use eye goggles when working with ammonia. Always ask permission when visiting a cemetery on private property.