Conservation Methodology

Some conservation specifications recommend squaring the bottom of the stone by cutting the stone with a saw. This is not recommended as the use of power tools on old stones can cause damage to the stone. In addition valuable history including inscriptions may be lost. If the bottom of the stone is not square a base with the same dimensions as above should be made but the slot should go completely through the base. This allows the excess stone to extend under the base level if needed and provides for better support.

Restoration mortar repair
Repairs to gravestones, generally involves reassembly of broken pieces and fragments of stone, filling open joints, cracks and delaminating. Depending on the stone and type of break will determine which method of reattachment.

Structural reattachment
Broken stones to be bonded should be carefully cleaned and dry fitted to insure proper fit. The area around the stone should be probe for any missing pieces which may belong to the stone. Traditional method of two part epoxy (Aboweld 55-22, Abatron) is the common way of bonding stones that require structural integrity. Epoxy is very strong although it also is moisture insensitive.

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This has the effect of creating a moisture barrier at the repair joint. For marble and slate stones this can cause stone degradation over time due to the inability of the moisture to wick away from the area. Field observations have shown that failures usually occur adjacent to the repair joint which has been attributed to the strength of the epoxy being stronger than the marble. Closer observations have shown that the stone at the new break is usually degraded. Epoxy should be reserved for conditions where high shear forces are acting on the stone. Several factors such as angle of break, thickness of the stone, weight and bonding surface area need to be considered when deciding to use epoxy.
For most bonding applications, a non polymer, cement based restoration mortar (Jahn Restoration Mortars, Cathedral Stone) should be used. The specific bonding method should conform to the manufacturer’s specifications for the specific stone and should be performed by a certified Jahn Products Technician. Bonding with restoration mortars is preferable since the mortars are permeable to moisture and allow the stones to breath. Over time the stone integrity is maintained and should last longer than the epoxy. Restoration mortars should be tinted to match the stone color and texture after cleaning. Tinting can be achieved through appropriate pigments (alkali stable oxides) which are available through Cathedral Stone or mason supply.