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All-time Practice Recommendations for Cleaning Regime Issued Headstones

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Jason Church demonstrates the top-down approach for cleaning headstones while in a cemetery.
Jason Church demonstrates the proper technique for cleaning a marble headstone using a biocidal cleaner, water, and a soft bristle castor.

NCPTT | National Park Service

This document was developed as general guidance for the cleaning of government issued headstones based on research undertaken past the National Park Service National Center for Preservation Applied science and Training and funded past the Section of Veterans Affairs National Cemetery Administration. Recommendations are intended to be used by cemetery directors, operations staff, foremen, maintenance staff, contractors and headquarters staff. The certificate focuses on general cleaning and regular maintenance of marble headstones that are soiled from dirt and biological growth. Recommendations do not address cleaning needs from unusual events such as removal of road tar, mower scars, vandalism, or other accidental impairment. Cleaning recommendations for other stone types such as granite, sandstone, or limestone are non presented here.

One of the critical components of maintaining the appearance of a national cemetery is the cleaning of headstones. Many of the more than 3 million gravesites in 131 national cemeteries are historic headstones and markers which should be protected and treasured. Also, today's new headstone will be tomorrow's historic grave mark.

Headstone cleaning must take into consideration the operational standards set along past the National Cemetery Administration.[i] The post-obit standards are amid those designated for headstones:

  • Headstones, markers, and niche covers are clean, complimentary of droppings and objectionable accumulations.
  • Headstones, markers, and niche covers are not damaged by cemetery operations (due east.g., interment, grounds maintenance, headstone, marker, niche cover, maintenance, and facility maintenance operations).

Maintenance practices must have an centre toward the futurity. Many cleaning methods may be able to remove soiling from headstones. Some will exist more effective than others. But the long‐term effects must also be considered. Anyone developing a cleaning method must await at the soiling agent to be removed, the potential threats acquired past the soiling, and the possible unintended results of cleaning.

Soiling Agents or Accumulations

Soiling agents are accumulations on stone that modify the appearance of the stone and may crusade additional harm. Different soiling agents may respond improve to a particular cleaning method. Soiling agents include:

  • Dirt, including soil and mud, often arises from transferring the topsoil to headstone surface. Dirt can lead to dark staining on the surface or an overall muddy appearance. Dirt can penetrate into the pores of the rock and be difficult to remove. Minerals containing atomic number 26 can leach into the marble surface and leave rust colored stains behind. If the headstone has sunk into the ground over fourth dimension, then is raised and realigned, a singled-out line of soiling can exist seen. Clay tin can retain wet afterwards rainfall and lead to the growth of mold or mildew on the stone surface.
  • Air pollution, including particles from vehicle frazzle, tin can deposit on the surface of marble. Nearby factories or industrial activities can generate pollutants that can alter the appearance of the rock or chemically interact with the rock over time. For example, sulfur dioxide produced through manufacturing processes and vehicle exhaust can interact with marble surfaces to cause gypsum crusts. These crusts tin can capture soil and pollution particles to create rough, grayness surfaces.[two]
  • Biological organisms, such as leaner, mold, mildew, algae, mosses, or lichen tin can adhere to the headstone and result in appearance changes. Microorganisms are capable of establishing a biofilm on the surface of the stone. Biofilms include proteins and sugars that are difficult to remove through standard cleaning practices and provide food for regrowth of organisms.[3] Bacteria can consume air pollutants and produce acids that tin attack the stone. Fungi tin penetrate the pore organisation of rock and deport leaner further into the rock.[4]
  • Bird droppings or other animal secretions can stain the stone. Depending on the beast'south nutrition, the stains may be hard to remove. Urine seeps into porous materials and with time produces yellow stains.
  • Constitute or tree sap is a pasty substance that drips from overhanging trees. The material may contain resins that are not hands dissolved in water. The sugars in the sap may attract insects or provide nutrient for molds and mildews. Shrubs accept falling berries that tin stain surfaces.

Other threats to headstones

  • Salt damage can cause disintegration of a stone surface. The presence of salts inside the rock, in the grounds surrounding the stone, in irrigation water, in some herbicides, and in some cleaners, tin can migrate through the stone'due south porous network and cause damage. Salts are dissolved and transported by water. They can recrystallize and exert pressures in the pores that may exceed the strength of the stone.[v, 6] Thus, practice not utilize cleaners that leave behind salts to clean marble headstones.
  • Freeze thaw cycles tin can increase rock weathering. Water can enter into openings, cracks, and pores of stone. If freezing temperatures exist, the h2o can freeze and expand. With many freeze thaw cycles, h2o can damage stone.[7] Since most cleaning efforts crave saturating the stone with water or liquids, do not clean headstones during freezing temperatures or when a freeze is expected inside 48 hours of the cleaning.
  • Improper cleaning can stain the surface or advance stone deterioration. Wellmeaning but ill‐informed custodians of cemetery headstones do damage through poor pick of cleaning methods. This would include utilize of power‐washing equipment too close to the stone, not rinsing later on awarding of cleaner, and and using products in a greater strength than the manufacturer recommends.

Important factors to consider

  • Use the gentlest, to the lowest degree invasive method. Select cleaning methods and materials that, to the best of your knowledge, do not affect the headstone. Chemicals and physical treatments should be undertaken using the gentlest means possible to insure the longevity of the headstone and to minimize the need to replace the stone.
  • Do no damage to the stone. Exercise no harm to the headstone during its care or the intendance of the cemetery. A headstone is placed on a soldier'south grave as a mark to identify burial site, merely serves other roles also. It is intended to honor the deceased and thus should be treated with respect. Over fourth dimension the headstone takes on meaning to the loved ones who visit. By its very nature, it possesses added value and clan to the veteran's service.
  • Consider long‐term effects. Recognize that cleaning efforts are function of a continuum of cleaning that will be applied to the headstone. All efforts to make clean headstones affect the surface in means that are non ever obvious. Marble is made up of interlocking grains of carbonate mineral which is bound together in a network that includes varying amounts of pores. When the surfaces are cleaned, some of the grains can be loosened and lost. Sometimes the mineral folder that holds the stone together can be afflicted. Over time and many cleaning campaigns, the surface can be altered noticeably and event in a sugaring appearance. Some marble is more prone to this blazon of deterioration than others. For example, Colorado Yule marble is more affected by cleaning than Cherokee White marble from Georgia.
  • Don't remove the original surface. The original surface may be polished and smoothen. The inscriptions are generally carved into the headstone. If the original surface is altered, the manner the headstone after weathers may be changed. As the surface roughens, it will soil more easily. The inscriptions can be eroded away, making the headstone harder to read. Never aggressively scrub the surface, or use wire brushes or mechanical methods such as sanders or grinders to clean the surface. Come across also –mechanical cleaning: power tools, below.
  • Minimize cleaning impacts. Minimize the number of times a headstone is cleaned in its lifetime. While a cyclic maintenance program is needed to maintain the appearance of the headstone, overcleaning should be avoided. If possible, celebrated headstones should not be cleaned more frequently than once a year.
  • Test cleaner starting time. ALWAYS Examination the cleaner for suitability and results before overall cleaning. Conduct the examination using the recommended application procedures. Let test area dry out thoroughly before inspection. When using a biocidal cleaner, information technology may accept several days before the full cleaning effect is realized. When applied, allow two or more weeks for biological soiling to disappear.
  • Consider Ecology Conditions. Environmental conditions may dictate the frequency of cleaning. For example, headstones that are located in shady and damp areas under trees may need to exist cleaned more than frequently than headstones in sunny areas.

Cleaning techniques known to harm stone

  • Bleach or bleach‐like products. Household bleach or other oxidizing cleaners, such equally Daybreak cleaner or HTH Shock 'Northward Swim pool treatment may chemically react with the stone surface and get out soluble salts in the pores of the stone which volition lead to decay. Cheque the label of the cleaner or the Materials Rubber Information Sheet (MSDS) for active cleaning ingredients. If the products contain sodium hypochlorite (NaClO), sodium perborate, sodium percarbonate, sodium persulfate, tetrasodium pyrophosphate, calcium hypochlorite or urea peroxide, do not use them for cleaning the headstone. For example, Daybreak cleaner contains xiv% sodium hypochlorite and is not recommended.
  • Strong acids or bases. Strong acids, including muriatic acid, hydrochloric acid, or others are too harsh and will dissolve the rock surface. Because they are corrosive, they can also be chancy to workers. Strong bases, such every bit concentrated ammonia, sodium hydroxide, calcium hydroxide, potassium hydroxide, or others may be aggressive on the surface of the stone and may be hazardous to workers.
  • Mechanical cleaning: Ability tools. Harsh mechanical devices such every bit sand blasting, or power tools such as sanders or drills equipped with a wire brush remove the original material of the grave marker.
  • Mechanical cleaning: Loftier‐pressure washing. Pressure level washing systems are mechanical sprayers that use h2o under loftier pressures to make clean surfaces. Commercially bachelor force per unit area washers operate at pressures betwixt 750 psi and 30,000 psi that volition damage marble headstones. This technique tin cutting into and mar the surface of the rock. The advisable distance and pressure level needed to properly clean an individual headstone is mostly almost 12 inches with a force per unit area of 500 psi or less. Some stones may not be able to tolerate these conditions depending on their condition. A test patch in a small-scale unobtrusive area on the headstone is recommended prior to cleaning.

Cleaning methodology

A cleaning regimen for headstones should exist based on ecology considerations such as humidity, biological growth rates, tree cover and vegetation, atmospheric precipitation and other factors that influence the frequency of cleaning necessary to maintain an advisable appearance.

  • Choosing the cleaner. Cleaning should exist undertaken with the mildest, to the lowest degree‐abrasive method. Improper cleaning can lead to accelerated deterioration or loss of original materials. Always begin by reviewing the Materials Data Safety Canvass (MSDS) for whatsoever chemical product to be used. The MSDS may be constitute by searching online or by contacting the manufacturer or distributor. The MSDS contains important chemical information and necessary safety precautions needed for apply of the production.

    Brand sure to note the manufacturer'southward application recommendations. The 2 near of import features to annotation are the dilution ratio and the dwell fourth dimension. If the manufacturer recommends diluting the cleaner, use the recommended dilution ratio. A small corporeality of the cleaner should be added to water to create the required ratio. Using the cleaner in a more concentrated grade may increment the risk of harm to the headstone. The dwell fourth dimension is the corporeality of time that the cleaner is left on the surface of the stone before scrubbing and rinsing the stone. The dwell time varies depending on the cleaner.

    Biocidal cleaners are available for apply on stones that have biological growth, such as algae, mildew, moss, and lichen. Well-nigh biocidal additives also help to keep biological from returning to the stone for an extended period of time. Recommended biocidal cleaners include D/2 Biological Solution manufactured by Sunshine Makers,2 Enviro Klean® BioWash®,3 or other cleaners that contain quaternary ammonium compounds. Consult with the production manufacturer to determine if the biocidal cleaner contains buffers that may leave salts backside on the stone. Follow directions as specified past the biocide manufacturer, making sure to rinse thoroughly. It is important to know that marble cleaned with biocides should continue to lighten over the next few days. The advantage of a biocidal cleaner is that it helps remove a wide range of soiling including biological growth. The disadvantage is that the cleaners are more than expensive than other products on the marketplace.

  • Equipment needed:
    • Personal Protective Equipment. While no special equipment is required under normal apply, gloves and eye protection are recommended. Avoid centre contact where splashing of the cleaner may occur, such as during spray applications. Launder hands thoroughly after treatment whatever cleaner and earlier eating, drinking or smoking.
    • Brushes. Soft bristle brushes are required when cleaning stones. They can have natural or synthetic bristles. Vegetable brushes or soft grooming brushes for large animals are a few that can be constitute in chain or farm supply stores. All rough or metal edges must exist covered with tape to reduce the chance of scratching the rock.
    • Paw or Backpack Sprayers. A multifariousness of hand‐pump sprayers tin can exist used for cleaning headstones. Brand certain that the sprayer is dedicated to the cleaners to exist used and not used for other functions similar applying pesticides. Haversack sprayers are useful when cleaning a large number of headstones typical in the national cemeteries. These consist of a holding tank, hose, and wand with adjustable nozzle. The sprayers more often than not operate in a 15‐80 psi pressure range.
    • Clean H2o. I of the about of import things to locate in the cemetery is the nearest source of water. It takes a lot of water to properly clean rock. If the cemetery does non have clean running water then it is important to bring barreled or bucketed water to the site.
  • Pre‐wetting the rock. Soak the stone liberally with water before applying the cleaner with a mitt or backpack sprayer. Stone is a very porous material and will absorb the cleaner. By soaking it beforehand, the cleaner will stay on the surface of the stone and minimize penetration of the cleaner in to the stone. This activeness minimizes potential agin furnishings past the cleaner, such equally common salt crystallization in the pores of the rock. It makes it easier to rinse the cleaner from the stone surface.
  • Applying the cleaner. Always keep the stone moisture during cleaning and thoroughly rinse afterwards. Do non allow the cleaner to dry on the stone. Apply the cleaner according to the manufacturer'south recommendations. Changes to the dilution or dwell time are considered "off‐characterization" and the effectiveness of the cleaning method cannot be guaranteed. Evenly apply the cleaner with a sprayer to saturate the surface.
  • Agitating the surface. Agitate the surface gently in a circular movement using a soft bristle brush. Work in pocket-size areas, starting from the bottom and moving toward the top of the headstone. Agitation will loosen soiling from the surface of the stone.
  • Rinsing the stone. Remember to rinse afterward cleaning each area and to thoroughly rinse the stone at the end to brand sure that no cleaner is left behind.

A typical cleaning regime may include a iii‐person team. The commencement person thoroughly wets the stone with make clean water using a hose or a portable haversack sprayer. A second person sprays the stone surface with the biocidal cleaner. After the appropriate dwell time, a tertiary person gently agitates the cleaner on the stone surface with a soft bristle brush, then rinses the stone with clean tap water.

Glossary of Terms

Ionic cleaner: A substance that aids in the removal of clay and serves as an emulsifier by bridging between water and oil. The substance is a long chain chemical that has a accuse on i terminal.

Not‐ionic cleaner: A substance that is similar to an ionic cleaner, except that information technology does non have a charge.

Surfactant: A chemical compound that is a surface agile agent. It reduces the surface tension between liquids that do not commonly mix together. It aids in the cleaning of a surface.

Biocide: A chemical capable of killing living organisms. Pressure washer: a mechanical sprayer that uses high‐pressure water to clean and remove clay and other accretions from surfaces and objects.

Dilution ratio: reduction of the concentration of a chemical past mixing with water or another solvent past a specific portion. A useful reference nautical chart for specific dilution ratios can be found at Tomorrow Chemicals (PDF).

Dwell time: The time a cleaner remains on the surface of a stone earlier agitation or rinsing.

References

  1. National Cemetery Administration, National Shrine Commitment, Operational Standards and Measures. October 2009, Section of Veterans Affairs: Washington, DC. p. 32.
  2. Charola, A.E., Review of the Literature on the Topic of Acidic Degradation on Rock. 1998, NCPTT Publication 1998‐09: Natchitoches, La. p. 85.
  3. Hall‐Stoodley, Fifty., J.Due west. Costerton, and P. Stoodley, Bacterial biofilms: from the Natural environment to infectious diseases. Nat Rev Micro, 2004. ii(2): p. 95‐108.
  4. Mitchell, R., The function of microorganisms in the deterioration of atmospheric pollutants of rock used in historic buildings and monuments. 1998‐1999, NCPTT Grant number MT‐2210‐8‐NC‐23: Harvard University. p. 23.
  5. Rodriguez‐Navarro, C. and E. Doehne, Common salt weathering: influence of evaporation charge per unit, supersaturation and crystallization blueprint. Globe Surface Processes and Landforms, 1999. 24(3): p. 191‐209.
  6. Scherer, G.W., Decision-making Common salt Impairment. 2009, NCPTT Grant No. MT‐2210‐09‐NC‐03: Princeton University. p. 20.
  7. Hall, C. and Due west.D. Hoff, H2o Transport in Brick, Rock, and Concrete. 2002, New York: Taylor & Francis.

Concluding updated: September 27, 2022