Comparative Study of Commercially Available Cleaners for Use on Federally-issued Headstones
Jason Church, Materials Conservator
National Center for Preservation Technology and Training
In 2004, the National Cemetery Administration (NCA) and the National Center for Preservation Technology and Training (NCPTT) (an office of the National Park Service) entered into an agreement to study the effectiveness of commercially available cleaners to remove biological growth from federally-issued marble headstones. The project goal was to test cleaning products for effectiveness and appropriateness and to make recommendations of products and methods best suited to both clean and preserve the headstones.
This study incorporates five national cemeteries that are distributed both geographically and climatically. Cemeteries included in this study are Alexandria National Cemetery in Pineville, LA; Bath National Cemetery in Bath, NY; Jefferson Barracks National Cemetery in St. Louis, MO; San Francisco National Cemetery, in San Francisco, CA; and Santa Fe National Cemetery, in Santa Fe, NM. Cemeteries were chosen to represent various regions of the National Cemetery Administration as well as different climatic zones.
Cleaners chosen for this study were user friendly, suitable for large scale cleaning studies, environmentally safe and cost-effective. NCPTT canvassed a variety of cemetery stewards in both private and NCA administered cemeteries to determine the variety of cleaners currently being used in the field. Products chosen for the study included surfactants, chelating agents, biocides, and offered a range of pH from acidic to basic. Five cleaners were selected including D2 Architectural Antimicrobial, Daybreak, Kodak Photoflo, H2Orange2 Grout Safe cleaner, and World Environmental Group’s Marble Cleaner. Water from the site was also used as a control cleaner.
The two main focuses of the study were to evaluate the biological regrowth properties of the cleaners and to monitor any chemical or physical change to the marble itself. To accomplish this task numerous tests were utilized on both headstones in the field and lab samples. Federally issued upright grave markers are cut from two main types of stone, a Colorado Yule marble and Georgia marble. Both of these marbles were included in the test to determine if the marble type played a factor in the stones durability to the cleaners and biological growth.
For the biological aspects of the study NCPTT partnered with the Micro Biological Laboratories of Harvard University. Before any work was preformed each headstone was swabbed. The culture was then sent to Harvard for analysis. This analysis identified biological growth types such as fungi, algae, molds, and mildews. With each identified type of growth a biological count was identified to show not only what was found on the stone but in what quantity. After the stone was cleaned it was again swabbed for any biological regrowth. This information was used to compare the biocide properties of the chosen cleaners.
Any physical or chemical changes in the stone were tested in a variety of ways. Each headstone and lab sample was photographed and colorimeter measurements were taken throughout the study for visual comparisons. Each of the cleaned headstones and lab samples were also analyzed using a portable X-Ray Fluorescence instrument. This is used to detect any residue such as soluble salts on the marbles surface. Marble core samples from the quarry were also treated with the cleaners then put through a QUV accelerated weathering instrument. These samples were mapped with a laser profilometer prior to and after treatment to determine any surface change caused by the cleaners. A variety of other analytical tests are being preformed to help determine any chemical changes in the stone.
The end result of this study is to provide the NCA with recommendations on which cleaner(s) may work best in each of the different climatic regions of the United States. The recommended cleaner(s) must have both the cleaning properties required by the NCA to maintain the National Shrine standards and cause no harm to the marble itself. This is important for long term cost effectiveness and to maintain the historical qualities of our National Cemeteries.