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Cleaning Most people begin a restoration project because they want to clean the gravestones and monuments to make them "look like new. But the cleaning needed to return them to this state will cause permanent damage and likely speed the natural weathering process. The distinc- tion of historic stones and monuments comes in part from the stains and evidence of natural weathering. When excessive cleaning pro- duces a "like new" appearance, the stone will lose some of its historic integrity. Only stones and monuments with sound structures and surfaces should be cleaned, because any cleaning will permanently damage . stones with flaking or peeling surfaces and structural weaknesses. And even then, you should clean sound stones only to halt deterioration or to remove heavy soiling. You should use the most gentle method possible. Avoid acidic cleaning solutions or solutions containing chlorine bleach. When you use water, avoid high pressure sprayers. Use something like an ordinary garden hose instead because that sort of pressure will probably not harm the stone. Avoid frequent cleaning; even the most gentle cleaning will remove some of the stone surface. First, use a natural or plastic soft -bristle brush to remove loose dirt and lichen. Next, use a toothbrush to clear away debris in carved niches. Once the loose dirt is removed, thoroughly soak the stone with clear water, then scrub the embedded dirt with the soft -bristle brush. Wash out the dirt and debris with clear water. This most gentle method will probably clean satisfactorily. If more cleaning is needed, dissolve a non-ionic detergent in water. This type of detergent will not deposit a solid, visible residue.' Thoroughly soak the stone with clear water, spray it with the non-ionic solution, then scrub with the soft brush. Finally, rinse it with clean water thoroughly to remove all trace of the detergent solution. You can find non-ionic detergents at photographic, conservation, and horse grooming suppliers. A solution of one part ammonia to four parts water can be used to clean marble stones. Never use abrasive cleaning methods. Dolomite powder, baking soda, and other household cleaning agents will erode the stone surface. In one day, a harsh cleaner can cause as much surface ero- sion as fifty years of normal weathering. Household bleaches like Clorox and Purex can damage even�polished granite. 0