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.