Cleaning Gravestones
CLEANING A GRAVESTONE
Non-ionic Detergents
Non-ionic detergents such as NP40, Triton X-100, Tween20 or The Kodak Companies Photo Flo are recommended by many experts for cleaning gravestones. These chemicals are electrically neutral cleaning agents that neither contain or contribute to the formation of soluble salts. They are neither soapy (normal soaps are Ionic detergents), nor do they affect pH. By decreasing the wash water's surface tension non-ionic detergents reduce droplet formation on the stones surface. In general they have been proven to provide a better overall wetting of the stones surface that other detergents and as a result, produce better results in the removal of general soiling.
Non-ionic detergents are available from conservation, janitorial, and photographic suppliers in various sizes. Photo Flo is the most common Non-ionic detergent. It is extremely concentrated and currently available in either 50ml or 500ml sizes. A recommended cleaning solution is one ounce non-ionic detergent to 5 gallons distilled water. If you do not use up all that you have made it will keep for about a month before it starts to develop "floaties" and will need to be disposed of. You may want to bring a small spray bottle of water for gently cleaning dirt and debris from the stone. Wash stone with solution, then rinse stone with clean water.
PRESSURE WASHING GRAVESTONES
THE CLEANING OF MARKERS OF HISTORICAL SIGNIFICANCE REQUIRE SPECIAL CONSIDERATION. IF THE MARKER YOU ARE ATTEMPTING TO CLEAN IS OLD OR APPEARS TO BE BRITTLE WE RECOMMEND YOU CONSULT AN EXPERT BEFORE ATTEMPTING TO CLEAN THE MARKER.
Pressure Washing of gravestones is a somewhat new and serious threat to cemeteries. A search of the internet will find hundreds of websites, all with a similar wrong message - "In most cases moss or most stains can be removed by pressure washing and professional cleaning". Most of these websites are for monument companies and seem to be making use of the same standard FAQ. One website goes so far as to imply that The Association for Gravestone Studies is aware and approves of the use of pressure washing for gravestones. However a quick glance of their website proves this not to be the case. Others still are for Cemetery Monument Restoration services - people that should know better than to use this method.
The National Center for Preservation Technology and Training (NCPTT) recently organized a seminar and workshop on the conservation of gravestones and other monuments commonly found in cemeteries. More than 60 participants from around the nation participated in the events held in Natchitoches, Louisiana. The participants represented a wide array of individuals involved in cemetery preservation, including cemetery association members, State Historic Preservation officers, national and state park employees, K-12 teachers who use cemeteries in their lessons, doctoral students con-ducting research in cemeteries, cemetery caretakers, monument builders, and family cemetery owners.
Following the conference, NCPTT held a two-day workshop including hands on condition assessment, safe handling procedures, and conservation treatments. The conservation treatments encompassed cleaning tests using water, hand scrubbing with soft-bristle brushes, chemical methods, and low-pressure washing (less than 600 psi).
The fact that they would recommend any type of pressure washing is of great concern. While this method may produce the desired results of a clean gravestone, MSSPI is strongly opposed to the use of pressure washing. There is simply far too much risk to the stone using this method. Any water pressure over 40 psi has the potential to cause significant damage to a stone, depending on the condition of the stone. A standard home garden hose with a nozzle attached will put out on average about 50 psi and the nozzle may actually cause the stream to be more direct than the stone can handle. The use of a pressure washing system on a gravestone will not only remove the outer surface of the stone, but expose the softer interior pores. These newly exposed pores will have a tendency to catch and hold onto grime and moisture that travel through the atmosphere. Trapped moisture within the stone from pressure washing will lead to a shorter stone life. If used on older stones, pressure washing can and will flake off entire layers of old brittle stone.
REMOVING LICHENS
To clear up a common misconception, lichens do not eat the rock, rather they naturally grow on stone surfaces that are available to them, whether these surfaces are naturally occurring or are artifacts of human activity. You will not be helping to preserve the stones by removing the lichen. The gray and orange patches formed by lichens on gravestones give a distinctive character to an old cemetery. These attractive "time-stains" not only enhance the appearance of the churchyard but are often of some rarity for which, like many other organisms, the cemetery is a wildlife sanctuary. Many lichens require a particular type of stone on which to live and, in many lowland districts, the cemetery may be the only undisturbed location in the area for many of these types of stones.
There are differing views as to whether lichens damage the stone on which they are growing or whether they protect it. There is evidence that the acid substances produced by lichens can attack the stone, but this effect is limited to a very thin layer immediately under the lichen. Any small cracks present or caused by this process will probably be infiltrated by the fine root-like hairs (fungal hyphae) of the lichen and this may cause more damage. It has, however, been argued that any damage caused by these processes is less than would be brought about by the weather if the lichen was not present. The tough, rather thick, lichen can protect the underlying stone from the weathering effects of wind, rain and frost. On some soft stones in exposed sites the lichens may eventually cover raised areas where the surrounding stone has been eroded away by natural weathering.
In some circumstances it may be necessary to remove lichens and various methods have been used with success. You'll never get a crustose lichen off a rock and keep the rock's surface intact. Lichens cause differential weathering on the rock which is visible as stains. On basic rocks the lichens will stain the rocks by their acids. The lichens also shield the rock from radiation which can lead to differences in color even on acidic rocks. If the purpose is to enable an inscription to be read, other ways of doing this should be tried first before the removal of the lichens. These methods, to increase the clarity of an inscription, include wetting or looking at it in the twilight with a torch shone along the inscription on a gravestone at a low angle. This will enable many worn inscriptions to be read. If it is deemed that cleaning is essential, only the minimum area necessary should be treated. This may be done by physically rubbing the lichens from the surface. Where this is done on a smooth stone the result may be unsightly as it is almost impossible to remove many crusty lichens from the lettering of the inscription. The lichens remaining in the lettering and cracks will probably regrow but rare lichens may have been lost from the surface. Another physical method that has been used is to cover the area to be cleaned with black polythene. It may take some months for the lichens to die but they may then be removed with a brush.
A homemade poultice an be produced using Dry porcelain clay mixed to a peanut-butter consistency with equal parts of water and glycerin. Small quantities of glycerin are available at most pharmacies; for larger quantities, search the Internet for soap-making supplies, floral supplies, etc. or check your Yellow Pages for "soapmaking supplies"; the large craft stores might carry it as well (Michaels, Hobby Lobby, etc.) Just be sure to stay away from "glycerin melt-and-pour" soap base. You'll need straight glycerin (you'll mostly likely find "vegetable" glycerin). Please be sure NOT to ask for NITRO-GLYCERIN. You will have every law enforcement agency in the country checking your personal history and watching your every move.
There is a new product, BIO-LICHEN OFF, produced by Sunnz International Ltd,
P.O. Box 13-598, Onehunga, Auckland, New Zealand that is said to be a fast acting and effective concentrated product designed to remove all Lichens, Moss and Fungal growth from most surfaces. More information can be found at:
Hydro Clean Restoration Cleaning Systems produces HT-777 for use in cleaning Marble. This is a product that when mixed with water forms a creamy, non- acidic paste that will remove both organic and inorganic stains from polished marble and other substrates, returning the stone to its natural color and hue. It is made from mild, biodegradable detergents, clays and powders and will not etch marble or any other polished surface. The product's "wicking" action allows the cleaning chemistry to pull out stains that are deeply set in the stone. HT-777's Poultice Additive is a liquid that contains additional detergents and wetting agents that will enhance the cleaning properties of the poultice. The product is easy to use and virtually odorless. Large areas can be cleaned at one time. Additional information can be found at http://www.hydroclean.com/data_sheets/ht-777.htm .
The Association for Gravestone Studies suggests that Calcium Hypochlorite (e.g., Chlorine, "HTH," "Shock Treatment") is effective for the removal of biological growth. It is a granular product that is not to be confused with "liquid chlorine" or sodium hypochlorite. Calcium hypochlorite is available from swimming pool suppliers. A suggested cleaning solution is one ounce calcium hypochlorite to one gallon hot water. Please keep in mind that this product should be used only when a waterhose with a good water pressure (e.g., 55 psi) is available. Any water pressure over 40 psi has the potential to cause significant damage to a stone, depending on the condition of the stone.
Whatever method is used care should be taken to treat as small an area as possible and not allow the chemicals to drip onto adjacent parts of the stone or statue. Before commencing try to get an experienced lichenologist to check that there are no rare lichens present. Remember, before you kill them, that these lichens may have been growing on the stone for many years.
This information was provided by www.savinggraves.org
You can learn more about cemetery preservation and research links at their website.