APPENDIX C

CONSERVATION OF GRAVESTONES

The visible parts of a cemetery consist essentially of monuments, generally of stone; the inscriptions upon them; and the setting and environment in which they stand.

Restoration and conservation of a cemetery thus includes the maintenance and conservation of the gravestones and inscriptions, as well as their actual surroundings. The following notes are divided into three sections corresponding to the three main classes of stone used in NSW cemeteries, viz, granite, marble and sandstone. Some of the comments can be carried over to rarer types of stone, such as slate, quartzite and basalt; but technical or professional advice should be sought where these stones are used.

1. GRANITE

Granite is a hard, crystalline, generally coarse—grained rock which takes a high polish that persists for many years. True granites are generally pink or grey, but monumental masons apply the term to other hard crystalline rocks, including so-called “black granites” which are generally rocks of gabbro type.

Most granites are almost immune to weathering. Some may gradually lose their polish. They will not generally be physically damaged by re-polishing, but:

1. It must be realized that a re—polished stone is no longer “the original”.

2. Loss of polish may indicate that the stone was poorly selected, and that cracks are actually developing within and between the constituent grains. In this case, physically handling the stone may cause serious damage.

3. In the case of “black granite”, loss of polish may be caused by solutions washed out of unsuitable jointing (especially Portland cement) above the polished surface. Replacement of such jointing with an inert filler is more important than re—polishing of the stone.

2. MARBLE

The term marble is applied by masons to any rock consisting dominantly of calcite (calcium carbonate), and includes limestones as well as true marbles. Calcite is white, but minor impurities can give marble colour —red, brown, grey or even black. All marble can be readily scratched with a knife or key, and the powder is always white.

Calcite is slightly soluble in rain—water, so marble gravestones always become rounded. The polished surface becomes rough because of uneven weathering of individual grains. To preserve the inscription in this situation, the carved lettering is filled with lead or a metal alloy, to preserve the sharpness of the writing. In time, however, the marble dissolves away from this lettering and the letters peel away from the stone.

This natural destruction is inevitable, but the process can be slowed to some degree by appropriate management.

The situations which lead to rapid erosion of marble are:

(a) exposure to exhaust fumes from cars and smoke from coal fires;

(b) growth of black moulds on the stone surface or green moulds just inside the stone;

(c) overhanging tree limbs, which may produce organic acids, and which act as traps for industrial fall—out which trickles onto the stone in conditions of misty rain or heavy dew.

Where marble is slightly more permeable than usual, problems can also result from sea spray blown inland, and from soil water (“rising damp”) entering through the base of the stone by capillary action. In these cases the stone will show fretting, blistering or spalling, usually in a band a small distance above ground level.

3. SANDSTONE

Sandstones are rocks consisting of sand—sized particles (individually visible to the naked eye) held together by natural mineral cements. White or brown sandstones usually consist mainly of quartz grains; grey and greenish sandstones usually have grains composed of very fine grained aggregates of mineral material. Quartz sandstones may fret and shed individual grains, but the grains themselves are extremely resistant. Other sandstones, however, may weather or decay evenly, sometimes by surface grains dissolving away, in a similar manner to limestone.

Sandstone deteriorates in similar ways to limestone, but rising damp is relatively more important. The amount of salt and industrial fallout is also important: in Sydney region, cemeteries near the coast show considerably greater deterioration of sandstone monuments than those 10—20km inland.

The Sydney quartz sandstone sometimes shows fretting at the apex of decorations, or in shoulders near the top of the stone. This may result from leaching of cementing minerals, caused by rainwater percolating downwards. In this case it is advisable to remove any overhanging tree branches, but use of surface consolidants (resins, silicones etc.) is not recommended.

In other cases a thick (1—3cm) layer of stone may spall off the surface of the monument. Again, the mechanism is not fully understood, but injection of a hydrepoxy consolidant may sometimes be justified here on the grounds that the surface will fall away entirely if left untreated. In the present state of the art, however, such consolidants must be seen as a palliative, not a solution to the problem.

4. SOME COMMENTS ON “ARTIFICIAL” PRESERVATION OF SANDSTONE

Where sandstone items are of extreme value, the only way they can be indefinitely preserved is by placing them under cover, in a controlled atmosphere, isolated from the natural ground surface and their “natural” environment.

Developments overseas now enable stones to be completely saturated in hard—setting resins, but there are four objections to the process.

The first is that it is irreversible; the second that it alters the stone’s appearance; the third that its long—term effects must still be suspect. Finally, is such action actually preservation, when the whole nature of the material has been changed, and its natural history (including deterioration) interrupted?

Similar problems arise in considering re-inscription of gravestones. To the extent that the words are important, they are best preserved by transcripts and photographs. Until the message is actually illegible, the stone is still “original”; re-inscription destroys this originality. In this case it may well be argued that relettering is a natural and traditional maintenance operation, and therefore more acceptable than use of consolidants. (There is a counter—argument that development and use of new maintenance methods is equally a traditional process in society!)

Technically, re-inscription does not always cause problems. The newer surface tends to weather faster than the older one, and this should be realized; but the “readable life” of the monument is almost invariably extended.

Different people and groups will react differently to the principles discussed here, and it is not suggested that there is a single “right” answer. Indeed, most people will conclude that the whole approach to conserving a gravestone will depend on the reason it is important, in the same way that techniques used will vary according to the nature of the monument.

5. REPAIRING DAMAGE OF VANDALS

One of the most important agents of tombstone deterioration is man. Vandals break stones and push monuments off their pedestals; and in some cases, still more damage is done by individuals attempting to set things right.

Two basic principles can be laid down. Firstly, never use Portland cement or plaster of Paris in repair work: both can react with stone, and cement can even spoil the polish of some “granites”. Secondly, never use iron or steel dowels or clamps in repair work - they expand when they rust, and can crack even the strongest gravestone or pedestal.

Where a stone is cracked across, it is best repaired by use of bronze dowels set in lead or mason’s putty. Some masons now use epoxy resin cements, both for setting the dowels and for sealing the crack. Note, however, that a special, waterproof grade must be used, or it will deteriorate with time: standard Araldite, for example, is quite unsuitable. There is a problem in use of resins in sandstone and marble, as it prevents moisture migration in the stone; it is therefore undesirable in situations where the stone is subject to rising damp, especially if it shows any signs of natural weathering.

In some cases, financial constraints are such that the only alternative to abandoning a cemetery may be to set the stones individually in concrete pedestals. If this is done, it is essential that the cement mix be made as waterproof as possible, by using a commercial waterproofing agent; that the base of the stone be underlain by at least 5 cm of concrete; and that the upper surface of the cement block be well clear of the ground, and slope away from the stone to shed rainwater.