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Evaluation of Cleaners for Government Issued Headstones
Mary F. Striegel, Ph.D. and Jason ChurchNational Park Service
National Center for Preservation Technology and Training
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NCA Maintains 3 million+ gravesites.
• NCA preserves historic headstones which are 50 years or older.
• Today’s marker is tomorrow’s historic headstone.
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NCPTT, a leader in advancing preservation technology, and NCA partnered to evaluate cleaners for marble headstones based on soiling and biogrowth.
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Headstone Soiling
• Dirt
• Air Pollution
• Biological Organisms
• Bird Droppings
• Plant or Tree Sap
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Micro-organisms• Bacteria: can
slowly cause stone loss
• Fungi: Can change visual appearance
• Algaes: provides the most visual changes
Fungi sample found on marker in San Francisco.
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The StudyPhase I (2004-2005)
• Define Goals• Choose Cleaning Criteria• Recommendations must
meet NCA National Shrine Standards.
• Evaluate commercially available cleaners based on:– Appearance– Biological Re-growth– Physical and Chemical
Changes– Ease of Use
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Bath National Cemetery
• Bath, NY
San Francisco National Cemetery
• San Francisco, CA
Santa Fe National Cemetery
• Santa Fe, NMAlexandria National Cemetery
• Pineville, LA
Jefferson Barracks
National Cemetery
• St. Louis, MO
Field Test Sites
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Definitions
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Selection of Cleaners:
Table 1. Chosen Cleaners are ordered from Acidic to Basic.
Cleaner H2Orange2 Grout Safe Kodak Photo-Flo D-2 Marble Cleaner Daybreak
pH 3.81 7 9.5 10.5 12.1
pH Acidic Basic Alcohol Chelate Solvent Surfactant Bactericide
D-2 9.5 X X
Daybreak 12.1 X
H2Orange2 Grout
Safe 3.81 X
Kodak Photo-Flo 7 X X X
Marble Cleaner 10.5 X X X X
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Implement Field Studies5 cleaners + water
1,440 test patches
240 stones
5 National Cemeteries
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Phase II (2005-2007)
• Monitor regrowthin the field for 18 months at Alexandria, Jefferson Barracks, San Francisco, and Santa Fe.
• Evaluate cleaning effects on test stone in the lab
• Elimination: H2Orange Cleaner and Kodak PhotoFlo and Bath National Cemetery
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Phase II Laboratory Tests
Accelerated Weathering Microscopy
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Phase III (2008-2011)
• Plan long-term monitoring at two of the four sites
• Alexandria, San Francisco, and Jefferson Barracks cleaned the study headstones since phase II
• Alternate laboratory study was devised at Harvard University
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Phase III Bio Lab Study
• Samples of Colorado Yule and Georgia White Marble
• Innoculated with A fungus, Aspergillus niger
• After 7 weeks, samples were cleaned
• Evaluated microbial growth at Day 1, Day 34, Day 41, Day 90, Day 127 and Day 188.
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Results
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Study Findings: Field Results
• Field studies showed:– Daybreak, D2, and WEG
Marble Cleaner performed well
– Kodak Photo-Flo was the first cleaner to fail in the field (greatest biological regrowth)
– H2Orange Safe Cleaner failed after six months at Jefferson Barracks National Cemetery (killed bacteria but left green fungi)
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ClimaticDifferences
Semi Arid Steppe: Santa Fe
Humid Subtropical: Alexandria
Mediterranean: San Francisco
Humid Continental: Bath Jefferson Barracks
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Location Differences• Sunny areas:
Biocidal effects last much longer.
• Shady areas:
Fungal growth is more likely to return.
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Study Findings: Lab Results
• Lab studies looked for chemical and physical changes on the stone.
• Lab studies showed:– Daybreak left significant
salt deposits on stone
– D2 initially left small amounts of salts on stone: later D2 was reformulated, no salts found on repeat testing.
– WEG Marble and Granite Cleaner left no salts.
Daybreak
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Study Findings: Biological Lab Results
• Further accelerated biological studies, after 188 days showed:
– Fungi regrowth on WEG samples
– No regrowth on D2 and Daybreak.
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Issues to Consider
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Other Threats to Headstones
• Salt Damage
• Freeze Thaw Cycles
• Improper Cleaning
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Preservation Practices
• Use the gentlest least invasive method
• Consider long-term effects
• Minimize cleaning impacts
• Don’t remove original surface
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Cleaning known to damage stone
• Bleach and Bleach like products
• Strong acids or bases
• Power tools
• Pressure washing
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Cleaner Factors to Consider
• Manufacturer’s Recommendations
• Dilution ratio
• Dwell time
• Biocidal Cleaners
• Lightening with time
• Temporary non-permanent color changes during cleaning
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Recommended Actions
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Cleaning Recommendations
• Use D2 Biological Solution or similar biocidalcleaner, following manufacturer’s directions. Do not dilute.
• Apply to WET stone surface using a sprayer.
• Gently agitate with a soft bristle brush.
• RINSE thoroughly with water.
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Cleaning Frequency Factors
• Research offers observations, but frequency of cleaning will depend on location and climate of individual cemeteries.
• Different locations will need different cleaning schedules.
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Spot Cleaning
• Minimize the frequency of cleaning the entire cemetery by scheduling spot cleaning on those headstones located in shady areas that exhibit more biological growth and soiling.
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Summary
• Of the five cleaners tested, D2 Biological solution was most effective and left no harmful residues.
• Daybreak is a bleach solution.
– Continued use of Daybreak will result in long term damage to headstones.
• Use of high pressure power washers can erode the surface and deteriorate headstone.
• Use of chemical cleaners can be successfully accomplished by a three-person team.
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