Tomb Maintenance

Historically at St. Louis Cemetery No. 1, the mortars and bricks were covered with protective layers of stucco. Unlike the mortar, most stucco mixes were hydraulic lime- or natural cement-based with an aggregate of sharp fine quartz sand. These more durable stucco layers protected the soft interior structural brick and clayey mortar from moisture and invasive plant damage, and provided a smooth appearance to the surface.

Over time, as a result of tomb subsidence and rising damp, thermal and moisture changes in the materials cause mortar joints to loosen and bricks to move. Stresses build up in the walls and small cracks develop in the stucco layer, generally in line with the brick courses.

With periodic maintenance, these cracks are easily repaired and stucco should be reapplied as needed. This periodic maintenance keeps the tomb sound for generations. More information is available on recommended stucco and mortar mixes.

Portland cement was not used in tomb masonry until the mid twentieth century. Today, many of the early tombs have been encased in hard, dense cement stucco, probably in the mistaken belief that once applied, maintenance would no longer be required. The mismatch of properties and the entrapment of ever-present moisture between the interior brick structure, the historic stuccos, and the modern cements, have created problems of incompatibility and have led to structural damage far in excess of the damage seen in tombs that were not repaired with cement. In addition to trapping moisture, cement-based mortar and stucco repairs typically cause through-wall structural cracking of the brickwork, and when removed, tear off the face of the damaged brick beneath the stucco.

Cleaning Marble Tablets & Sculpture

A monument which is darkened with soiling, biological growth and metallic staining, is not only disfigured, but also is susceptible to masonry deterioration and, therefore, requires cleaning. A lightly soiled monument with legible details, however, does not require a major cleaning. All cleaning methods must be tested in a discreet location for each monument before full-scale treatment begins and all but the simplest methods should be left to the professional. The gentlest method should be tested first to avoid unnecessary damage. Fragile, bowed tablets should not be cleaned prior to stabilization.

Water washing is the gentlest, safest, and least expensive method for cleaning masonry and may be performed by the nonprofessional provided the tomb or stonework is sound. Most general surface soiling and some biological growth are easily removed with water. All open joints must be repaired first, to prevent penetration of large quantities of water into the masonry. The water should have a low metals content to avoid staining. Usually, potable water is adequate. Water can be applied at low pressure with a garden hose spray and may be supplemented by gentle scrubbing with nonmetallic soft bristle brushes and household detergent.

Much of the black staining occurring on tomb marble and stucco is not atmospheric soiling, but fungal growth. This can be most effectively removed after wet brushing by applying a 2-5% solution of calcium hypochlorite as found in commercial pool chlorine (2-5 parts dry powder to 100 parts water by volume) mixed with an inert clay such as talc or kaolin or paper pulp as a poultice. Once dry this can be removed by brushing and the surfaces well rinsed with a hose or pressure washer. Proper safety precautions must be taken as this material is a strong oxidizing agent. Eye and skin protection is required.

Since black gypsum crusts, resulting from the interaction of the marble or limestone with acidic atmospheric pollution, are water soluble, they may be removed with a slow water soak. For this method it is most important that all joints and seams are watertight to prevent the introduction of water to the tomb interior. Necessary drainage is critical to avoid water collection. As slight brown or yellow oxide stains can develop on certain stones possessing iron impurities, tests should always be done first.

Many commercial chemical products are currently available for cleaning, based on acidic and alkaline compounds and detergents. If used improperly, these can cause etching of stone, insoluble residues, and can introduce harmful salts which can further stone decay. Use of such cleaning systems is best left to experienced professionals.

Abrasive cleaning involving any grit or aggregate applied under pressure should not be used on stucco, brick, or friable stone. The technique is too aggressive and can cause irreversible damage to historic fabric. Abrasive cleaning can lead to accelerated weathering by pitting the surface, thus opening the masonry to increased moisture penetration, atmospheric reactivity, and subsequent deterioration. Basically, any method which removes stone should be avoided. Only an experienced conservator should perform such specialized cleaning methods and only after individual tests have been performed.

Vegetation & Landscape Issues

As in the case of domestic architecture, a range of garden features, such as planters, accompanies the various types of tomb that have developed in the cemetery. Used for both visual and olfactory decoration of the tomb and cemetery as a whole, gardens played an important role in the design of the tomb, and specialized plant palettes encoded with the language of mourning were used as part of this design.

Family memories and documents may describe the traditional flowers used in the planters and to make the immortelles placed on the tomb for All Saints’ Day and other special occasions. If the precinct has not been paved over, consider re-establishing the grass and shell ground cover and replace plantings that once existed. Plants and trees with invasive roots should be avoided, as they can damage tomb masonry.

Caution must be taken with power equipment near masonry or iron work. Grass and ground cover should be cut with nylon filament trimmers only. Do not use herbicides as they can cause deterioration of masonry and corrosion of metals, in cases where contact might occur. When considering major restoration work, do not undertake any interventions that create a discordant appearance in the cemetery landscape, such as the repaving of the precinct with concrete Covering the surface with cement serves to reduce the ability of the ground to evaporate moisture, but does not change the fact that the ground water is right below the tomb providing a ready source of moisture for rising damp. The interior structure of highly porous bricks, with numerous capillary sized pores, are powerful water absorbers and will overcome gravity to pull ground water into the structure.

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