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.
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).
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.
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
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 Cemetery
|
Zep
Ring Master All Purpose
Bathroom Cleaner
|
Spot
cleaning as needed
|
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 Cemetery
|
50%
Clorox and 50% water
|
Annually,
with spot cleaning as necessary
|
Applied
with pump sprayer, or Backpack sprayer. Left un-rinsed.
|
San
Francisco National Cemetery
|
40%
Clorox Outdoor
and 60% water
|
Total
cleaning once a year with pressure washing
as needed
|
Applied
with portable sprayer. Left un-rinsed.
|
Alexandria National Cemetery
|
HTH
Granular, mixed
with water to an
unknown concentration†
|
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.
6 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).