2. Background

The Department of Veteran Affairs provides patient care and veteran's benefits - including burial-related entitlements - to 70 million veterans and eligible family members. An agency of the Department of Veteran Affairs, the National Cemetery Administration maintains 3.6 million occupied gravesites in its 120 national cemeteries and 33 soldiers lots, which total more than 14, 250 acres.

Visitors to national cemeteries expect to find the burial grounds well-cared-for and looked after. Part of this expectation is that the headstones are well-aligned and display a pristine, white appearance. These beliefs lead to relatively frequent cleaning of federally issued headstones, particularly compared to cleaning efforts undertaken in private cemeteries. Over time national cemetery staff and visitors have noticed a deterioration of stones from weathering. When headstones show significant loss of legibility or deteriorating conditions, the headstones are replaced.

One contributing factor to the weathering of stones may be the selection and use of chemical cleaners on a regular basis. C. Price notes that cleaning is one of the first steps in the conservation of stone and leads to improved appearance. However, cleaning with unsuitable cleaning methods can damage the stone by the loss of surface, staining, deposition of soluble salts, or making the stone more vulnerable to pollution or biological growths.¹

Within the fields of conservation and historic preservation, guidelines for the care of cultural resources, such as cemetery headstones, have been established based on ethical considerations.^{2, 3} First and foremost, a conservation treatment, such as cleaning, should do no harm. Staff and volunteers undertaking the cleaning should choose the gentlest and least invasive methods. Guidelines also recommend that those undertaking the work should not use chemicals without thorough understanding of how those chemicals react to the materials of the artifact and any material that may have been applied later.

On December 16, 2003, the National Cemetery Administration took the lead to organize an interagency task force to develop solutions to shared issues of interagency responsibility for historic government-provided headstones in an effort to supply consistent service to the American public in keeping with agency policy and mission. Topics included definitions of what is "historic," the science and technology of appropriate cleaning, and when to repair or replace. One outcome of this task force was the identification of the need for scientific research on cleaning methods for headstones.

Based on observations in national cemeteries, documentation in conservation literature, ethical considerations, and recommendations of the Interagency Task Force on Government-Issued Headstones, this research study was devised through collaborative efforts of the National Cemetery Administration and the National Center for Preservation Technology and Training.

2.1. Purpose of Study
On September 13, 2004, the National Cemetery Administration and the National Center for Preservation Technology and Training entered into an agreement to study the effectiveness of commercially available cleaners to remove biological growth from federally-issued 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. Cleaners in this study are evaluated based on multiple criteria to include:

• Appearance immediately after cleaning and over time,
• Physical changes to the stone, such as surface roughness or porosity,
• Chemical changes to the stone, such as chemical interactions with the cleaners or residual chemicals left on the stone,
• Biological activity after cleaning and over time, and
• Ease of use and suitability for large-scale cleaning projects.

Phase one of the study includes the selection of cleaners and national cemetery test sites within five NCA regions or Memorial Service Networks. One aspect of the research looks at chemical cleaners that represent a variety of cleaning actions, for example basic versus acidic cleaning or ionic versus non-ionic cleaning. The research includes different geographic and climatic regions, such as a semi-tropical versus a dry or temperate climatic zone. Finally, cleaners are tested on two different types of marble - Colorado Yule marble from Marble, Colorado and White Cherokee marble from Tate, Georgia.

Five cleaning products are tested in side-by-side test patches on headstones in sunny and shady areas of each cemetery. Concurrent with the test patch studies, a series of cut marble samples are treated with each of the five products and exposed beside the test patch stones. These samples are used in both non-destructive and destructive laboratory testing. These laboratory samples help detect residual cleaning products on the stone and aide in evaluating potential stone deterioration.

Phase two of the study is based on results of the test patch evaluations after at least nine months of study. Based on phase one, three cleaning products are further tested on whole headstones. Whole stone studies allow for further evaluation based on visual appearance and ease of use.