Marble contains the mineral Calcite, a carbonate which reacts with acid, ie acid rain, making it susceptible to natural weathering. To letter marble, the inscription is carved and then small drill holes are made in each letter. Lead is then gently tapped into the letter and cut flush with the face of the memorial and the drill holes act as an anchorage system to hold the lead in. Contrary to marble, the lead is not affected by the acid rain, so does not erode, which leaves the lettering, over time, to stand proud and occasionally fall out as the weathering away of the marble thins the drill holes. Regrettably, because of the effect the weather has on the drill holes it is not possible to just tap the fallen letters back into the original carved letter – therefore the only way that the memorial can be renovated is to remove all the existing lead, and polish down the face and then re-letter and refill. Although marble is very good for carving, which is why many headstones made of this are very elaborate, it is not a material that has longevity. However, do not be disheartened; if you have a memorial in this material, it is possible, in 95% of cases, to have the inscription re-cut and the memorial professionally renovated.
Granite is an everlasting material, therefore it is lettered very differently to marble. Once the inscription is cut, the desired colour is simply applied to the letters. An inscription carved in granite will never have to be re-cut. The only remedial work that may need to be carried out is the reapplication of the gold leaf or paint, as over a period of time it will begin to flake away.