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Headstones were photographed before cleaning and at six month intervals after cleaning throughout phase one of the study. All photographs were taken digitally and saved in JPEG format. Photographs were taken in October 2005, April 2006, and November 2006.

In October 2005, photographs were taken using a Sony DSC-S85 digital camera. The camera has a built-in 34 mm-102 mm zoom lens. All images were taken at 2272 x 1704 pixel resolution on auto-exposure and auto-focus settings.

All subsequent photographs of headstones, taken in April 2006 and November 2006, were taken with a Nikon D50 digital camera body fitted with an AF-S 18-55 mm zoom lens. Images were captured at 3008 x 2000 pixel resolution (Large, JPEG Fine) at an approximate 45 mm lens focal length.

Appendix A, Photographic Documentation of Field Trials, contains a series of photographs taken in six month time intervals each headstone in phase one of the study. An overview shot and details of each test patch are found for each headstone prior to cleaning and every six months as the study progressed.

Jason Church positions the head of the Minolta colorimeter for measurements on a headstone in Alexandria National Cemetery.
Figure 2. Jason Church positions the head of the Minolta colorimeter for measurements on a headstone in Alexandria National Cemetery.

Upon completion of the photo-documentation, color measurements were taken using a Minolta Colorimeter, CR-400. Each measurement was repeated three times on each stone sample and averaged in order to compensate for slight variations in surface texture. Color measurements were consistently taken at the same locationñ the lowest point on the inside corner ñ within each grid (see Illustration 1).

The circles indicate the location where color measurements were taken within each test grid. Illustration 1. The circles indicate the location where color measurements were taken within each test grid.

Appendix B, Color Measurements on Field Trials, provides measurement data for all color measurements taken on headstones in the field.

3.5.2. Initial Biological Activity

Initial biological activities were determined by culturing swabs taken from selected headstones within each cemetery. The purpose of these analyses was to establish the level of biological activity prior to any cleaning performed in this study.

Figure 3. Photographic detail showing an acetate template being used as a guide for swabbing the headstone.Samples were collected by Jason Church from the five chosen cemeteries. Within each cemetery, samples were collected from 20 locations. A three cm2 area of the tombstones were sampled for microorganisms using BBL Culture Swabs (Becton-Dickinson, Sparks, MD). Samples were shipped overnight to Harvard University.

Figure 3. Photographic detail showing an acetate template being used as a guide for swabbing the headstone.

Results from this study are found in Appendix D, Analysis of Microorganisms on headstones in VA Cemeteries, First Report: December 2005 is summarized here. Bacteria and/or fungi were found in most samples in all five cemeteries. Algae, which are photosynthetic organisms capable of darkening or staining the headstones, were not found in samples taken during this phase of the study. The decreasing order of biological activities was:
Santa Fe > Jefferson Barracks > Alexandria > San Francisco > Bath

Santa Fe National Cemetery displayed the largest amount of bacterial and fungal activity of the five cemeteries, which was five times greater than any other location. Jefferson Barracks results showed small quantities of fungal growth on all but one headstone. Fungi were found on headstones in both sunny and shady locations. Bacterial counts were limited to a few headstones in Jefferson Barracks. In Alexandria, more bacterial and fungal activity was seen on headstones in shady locations over sunny locations. Bacteria were not detected in many samples from San Francisco National Cemetery, but when found, were more likely to be seen in sunny locations. In contrast, bacteria and fungi were detected in few samples from Bath National Cemetery.

Initially, the presence of higher biological activity at Santa Fe National Cemetery seemed counter-intuitive. Santa Fe is a drier climate and little biological soiling had been observed in the cemetery. Locations such as Jefferson Barracks or Alexandria would be expected to have richer environments for biological growth due to their climates and higher relative humidities. Additionally, a visual survey of private cemeteries in these regions showed typical biological growth, see Figure 4.

Figure 4. Example of biological growth found on a grave Figure 4. Example of biological growth found on a grave marker in the Jewish Cemetery, Pineville, Louisiana which is located four blocks from Alexandria National Cemetery. It is important to note before evaluating results from initial biological analyses that each cemetery has its own regular maintenance schedule which will influence the nature of the biological activity on headstones from that cemetery. Jason Church documented the cleaning activities of each cemetery by interviewing staff and maintenance crews (see Table 5).
Cemetery Cleaner Used Periodic Schedule Methods
Santa Fe National
Zep Ring Master All
Purpose Bathroom
Spot cleaning as
Applied with
portable sprayer and
rinsed thoroughly
Jefferson Barracks
National Cemetery
50% Clorox and
50% water
Annually Applied with pump
sprayer, or
Backpack sprayer.
Left un-rinsed.
Bath National
50% Clorox and
50% water
Annually, with spot
cleaning as
Applied with pump
sprayer, or
Backpack sprayer.
Left un-rinsed.
San Francisco
National Cemetery
40% Clorox
Outdoor and 60%
Total cleaning once
a year with pressure
washing as needed
Applied with
portable sprayer.
Left un-rinsed.
Alexandria National
HTH Granular,
mixed with water to
an unknown
Annually, with spot
cleaning usually 8
months after
Applied with
portable sprayer.
Left un-rinsed.

Table 5. Cleaning schedules and use for Santa Fe, Jefferson Barricks, Bath, San Francisco, and Alexandria National Cemeteries.

Santa Fe National Cemetery cleans headstones infrequently using a highly acidic product, Zep Ring Master Bathroom Cleaner6 for spot cleaning. Since the cleaner is a green liquid Santa Fe maintenance workers rinse thoroughly after cleaning. Jefferson Barracks National Cemetery cleans headstones annually using a 50/50 mixture of Clorox and water. The cleaner is applied with a backpack sprayer and left un-rinsed. Bath National Cemetery follows a similar cleaning regiment, cleaning once a year with the 50/50 Clorox mixture and following with spot cleaning as necessary. The cleaner is applied by sprayer and not rinsed after cleaning. A 40/60 mixture of Clorox Outdoor and water is used by the San Francisco National Cemetery to clean headstones using a portable sprayer. Headstones are not rinsed after cleaning. Alexandria National Cemetery uses HTH Granular, a calcium hypochlorite product commonly used for swimming pool treatments, to clean headstones.

Upon closer consideration of the data and the cyclic maintenance undertaken at each cemetery, logical conclusions could be drawn. This study did not begin with sterile stones inoculated with similar bacteria, fungi, and algae. The biological activity is a complex system influenced by seasonal changes, a variety of biota, the nature of the stone, and the history of headstone cleaning at each cemetery.

Santa Fe National Cemetery staff rarely cleans its headstones and then they undertake only spot cleaning as needed. Thus, a rich bio-film has developed over time on headstones in Santa Fe. Despite this biofilm, the stones appear clean because there is a lack of algae ñ the photosynthesizing organisms that can produce staining ñ or low numbers fungi.

In contrast, those cemeteries whose environments are likely to promote biological growth, such as Alexandria National Cemetery or Jefferson Barracks National Cemetery, are cleaned much more frequently in order to keep the stones white. In these places, HTH Granular (calcium hypochlorite) or bleach (sodium hypochlorite) is used for cleaning and left on the surface. After several cleaning cycles, the stones show much less biological activity.

The following general conclusions can be drawn:

  • Bacteria and/or fungi were found in most samples.
  • Numbers of bacteria were generally greater than numbers of fungi.
  • Algae were not detected in the samples.
  • Analysis of microbial growth showed wide variability in the size of the microbial community.
  • Numbers of bacteria and fungi were low in most samples and may be due to the historical cleaning cycles the stone has seen.
  • The presence of high numbers of bacteria and fungi at Santa Fe National Cemetery is likely due to its infrequent cleaning.

According to the published Materials Data Safety Sheet, Zep Ring Master has a pH of less than 1.0 and contains phosphoric, hydrochloric, and sulfuric acids (which can cause sugaring and loss of binder in marbles and limestones).

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One Response to Comparative Study of Commercially Available Cleaners for Use on Federally-Issued Headstones

  1. Nancy Scheer says:

    June 22, 2010

    I am interested in knowing if anyone has done any investigation into the affect of wet grass & weeds, thrown by lawn mowers onto tombstones?
    Does this cause some of the biological growths we see on tombstones?
    I see this often in cemeteries particularily when the grass has been cut early in the morning while it is still wet.

    Is there any data & results showing a “diluted solution of ammonia” for cleaning tombstones? I believe I read where it is not very effective on biological growth, but is it a recommended product for general cleaning of headstones?

    When using D2 do the rules apply that say only clean tombstones once every 10+ yrs? Where did this rule come from? I just read it on one of the National Preservations of tombstones sites. Is there data to back this rule?

    Has there been any conclusion to the National Cemetery Headstone Cleaning Project and if so where can I find the results?

    Thank you for any consideration you give to these questions.

    Nancy Scheer
    (a volunteer tombstone cleaner in Missouri)

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