It is necessary to clean a gravestone before performing conservation procedures. The appearance and legibility of many markers can be dramatically improved by washing with water and medium bristle brushes. A good source of clean water is very important is a conservation project. It is necessary to gently remove biological growths such as algae and lichen because they trap moisture against the stone. Pressure washing of the soft markers (marble, sandstone, and slate) should be avoided due to the adverse and irreversible effects of this method. Only a very few cleaning products are safe for use on marble, slate or other types of stone gravemarkers.
This is a basic procedure to prevent serious damage to tilting markers. It involves excavation of the stone and resetting in a sand and peastone mixture which provides the proper support and drainage. In no case should slate, marble or brownstone fragments be placed in concrete due to the deleterious effects of this method. Stones currently set this way often are left as is, since attempts to free the marker usually are more detrimental in the short run.
There are a very limited number of adhesives which have proved efficacious for use on stone existing in the uncontrolled environment, particularly slate.
Motaring into a base
This is the process for resecuring markers into bases from which they have come loose. It utilizes the same type of soft mortar mentioned in the discussion of cast bases. Concrete should never be used for this procedure. Instead, soft, high lime mortar is employed.
Capping, grouting, drilling, and blind pinning are other repair procedures which are utilized to conserve gravestones. Some require the availability of an electrical source in order to permit proper completion.