Restoring a headstone is important to retain legible information for future generations. Proceed with caution to prevent any damage that could be caused through the use of harsh chemicals. Acidic cleansers can adversely affect the inherent minerals and salt composition of the stone. Each headstone must be carefully examined to ensure its basic soundness before initiating restoration work.
Headstones are made of several different materials and may be soiled with various substances. Evaluation of each stone is necessary to ensure its safe and successful restoration. Most gravestones are granite, slate, limestone or marble. Acidic cleaners should be avoided with limestone and marble as these soft stones are easily dissolved by acid. Cracked or eroded stones should be cleaned by a stone restoration specialist to avoid inflicting further damage to the monument.
Cleaning should begin with a gentle rinsing with cold water and a light scrubbing with a cordless rotary tool outfitted with a nylon brush accessory. Testing a small, out-of-the way area is recommended before tackling the entire surface. Chemicals should be employed as a last resort and in highly diluted form to avoid damaging the stone. To avoid streaks, the stone should be cleaned at the bottom first and rinsed often to remove any dripping residue.
Avoid using a sealant on stone monuments. Clean stone only when the danger of frost is past. Freezing and thawing of water absorbed into the stone can initiate cracking. Do not use soap or any chemical containing sodium or abrasives. Highly mineralized water or water applied with extreme pressure can damage stone. Use distilled water if available and never employ pressure washing devices. Read the label before using any cleaning product, but never trust that all ingredients have been listed.
Look for non-ionic detergents at photographic or janitorial suppliers. These products are free of soluble salts and do not contribute to their damaging formation. One ounce of non-ionic detergent mixed with 5 gallons of water forms a suitably diluted cleaner. Household ammonia and calcium hypochlorite in heavily diluted concentrations are safe to use on marble and limestone. Coating a moistened headstone with absorbent clay, covering it to reduce evaporation and rinsing off the clay after 24 hours can safely remove some stains. This process, called poulticing, is safe for all stone types.