The primary concern in phase one was the biological aspects of the cleaners being tested.
The end of phase one was concluded with the removal of two cleaners due to their poor
biocidal properties. Phase two is primarily concerned with testing to see if the remaining
cleaners have any adverse physical or chemical effects on the marble. This will be tested
in three studies; the first will be on whole headstones cleaned in the field, the second is
testing on the sample stones that were treated and weathered in the cemeteries and the
third is a the continuation of the accelerated weathering studies done at NCPTTís
laboratories.
4.1. Laboratory Testing
Laboratory testing in phase two of the study evaluated two groups of samples. The first
group to be tested is laboratory samples that were treated with the select cleaners while
going through an accelerated weathering phase in a QUV weatherometer. The second
group to be tested is sample stones that were treated and weathered in the select
cemeteries for the past 18 months. These stones were recently removed from the
cemeteries and sent to NCPTT for testing.
Samples from both the laboratory study and the field test will undergo similar treatments.
The first series of tests will look for any severe deterioration of the stones structure (such
as surface loss) or discoloration of the surface. This includes photographic comparison,
colorimetery measurements and laser profilometry among others. The next series of tests
will look for soluble salts or other chemical residues left on the marble due to the
cleaners. The marble will undergo a series of destructive and non-destructive testing.
Preliminary destructive methods of testing for soluble salts include electrical conductivity
and various gravimetric methods. The presents of soluble salts inside the marble changes
the stoneís pore structure. This change has negative effects on the way the stone will
weather overtime. Methods used to test the two marble types for pore change include;
mercury intrusion porosimetry and nitrogen absorption porosimetry. X-ray diffraction
and XRF spectrometry will also me performance on the samples to help determine any
chemical contamination to the stones. The level of testing will be determined by the
amount of information found in the preliminary tests.
4.2 Whole Headstone Cleaning
Phase two of the study began by cleaning whole headstones in each of the five test
cemeteries. In the fall of 2006 Jason Church traveled to each of the sites beginning with
Bath National Cemetery on November 7th and ending with Alexandria National Cemetery
on January 16th.
To begin this phase of the study, the remaining three cleaners ñ D/2, Daybreak and WEG
Marble Cleaner ñ were used evenly to clean a total of 24 whole headstones in each
cemetery. Of the 24 markers half are Colorado Yule marble and the remaining half are
Georgia marble. For comparison purposes half of the stones were sprayed with the
cleaners and the other half was physically agitated. Before any cleaning was done the
headstones were first photographed and colorimetry measurements were taken. This
information will be used to compare the stones appearance over time.
When whole headstones were cleaned, each of the manufactures recommendations were
followed. Headstones were always cleaned from the bottom to the top starting with the
face and proceeding around the stone counter clockwise. After the cleaner was applied
and had significant dwell time, headstones were rinsed thoroughly with water from the
site. In the cases where headstones were only sprayed with the cleaner, a Cepia 1-touch
motorized sprayer was used. This 32oz handheld powered sprayed helped to control the
amount of cleaner used and regulated the force in which the cleaner was applied.
Remaining headstones were cleaned using agitation. The cleaner was first applied to the
stone using the motorized sprayer. Then the cleaner was agitated in a small circular
motion starting from the bottom and working up using a soft natural bristle brush that
measures approximately 3î by 9î. After the surface of the stone had been evenly
scrubbed the entire stone was rinsed.
During the next round of cemetery visits which will begin in May of 2007 photographs
and color measurements of the cleaned headstones will be taken. These will be used to
compare any change over time. Also, during this visit a measurement will be taken of
each of the headstone using the portable XRF spectrometer. This will help determine if
any of the cleaners left behind residual chemicals.