Do Not Migrate

This lecture is part of the 2009 Nationwide Cemetery Preservation Summit

Comparative Study of Commercially Available Cleaners for Use on Federally-issued Headstones by Jason Church

As Mary Stein here just walked by, we compared a study that NCPTT has began, several years ago now. It’s been a ongoing study for many reasons, we’ll talk about that. What we wanted to do was look at the national cemeteries, which is what we’ve been talking about. The NCA administers about 3.6 million grave sites. The big issue is a loss of legibility or deterioration in conditions that lead to the replacement of the headstones.

One of the issues that was brought to us … That better? Okay. One of the issues that was brought to us is, due to possible harsh cleaning techniques, a lot of the VA stones were being replaced more often than need be. There were looking at it both as an economic issue, but also of course as well that these are very important objects of cultural heritage. Cleaning may accelerate the stone’s weathering. Unsuitable cleaners can damage the stone by lost surface, staining, or the deposition of soluble salts.

Cleaning may accelerate stone weathering

Cleaning may accelerate stone weathering

The ideal cleaner that we’re looking for is one that does no harm. One that is the gentlest and lest invasive method, leaves an acceptable appearance. Remember we talked about and Dezzie talked about in her talk, this idea of an national cemetery. How it should look and how the visitors and loved ones really thing about it. It’s a very important aspect to the cemetery. We don’t want to leave salts behind. We don’t want to alter the chemistry of the stone’s surface. We were hoping to find things that might be similar in PH to the stone and wouldn’t alter the physical properties of the stone such as the stone roughness or porosity, and slows biologic regrowth.

One of the things that was brought to us is maintenance cost is a big issue. “Is there something we could find that our cleaner’s also instead of cleaning annually or semi-annually, or some places four times a year, could we stretch that out in any way?” Also a ease of use. Most of these cemeteries have a very small staff. As burials slow, as the cemetery fills up, your staff goes down. For example, Alexandria National Cemetery … Which is actually in Pineville, Louisiana. When we started this study it had a staff of two, so you’re looking at just a few people to oversee a lot of headstones to a very strenuous system.

That was one of the things that they wanted to know was, “Is there a way that we could clean less often? Easier to use as well.” The goals of the project were to evaluate commercially available cleaners. We didn’t want to reinvent something. We didn’t want to come up with our own. We wanted to look at what was already out there and look at those based on appearance, biological regrowth, physical and chemical changes to the stone, and the ease of use. This is one of our test sites with our signage explaining that the stones may look a little dirtier in our access study because they’re a part of the study.

The field studies we wanted to include five different climatic regions of the US. We realized that maybe one cleaner wasn’t going to do it all. One cleaner might work well on a cold environment than more humid environments. We wanted to look at those aspects. Also, environmental conditions. In that we looked at stones that were out in full sight and ones that were shaded to see how the cleaner effected that. Also stone types. Currently I believe there’s three main quarries that supply VA stones. We looked at the two main ones which are Georgia Marble out of Tate, Georgia and also Colorado Yule Marble is coming out of Marble, Colorado. We wanted to see did the cleaners have any different effects on the two marble types. Did that have anything to do with it?

Field studies including different climates, environments, and stone types measure color, biological activity, visual appearance, and chemical deposits.

Field studies include different climates, environments, and stone types to measure color, biological activity,
visual appearance, and
chemical deposits.

In doing these field studies, we wanted to measure color, biological activity, visual appearance, and chemical deposits. What you see in this photo right here is some of our field studies out in the cemetery. We did studies on some of the actual grave markers themselves and also we planted our own stones that came from the quarries that we could treat the same and then send back to destructive testing to determine that later. The laboratory studies that we’ve done included both artificial weathering, and we’ll talk more about that. Macro and micro analytical techniques. We did it both in the field and on laboratory marble samples.

What we did there is we took the two kinds of marble from the quarries and we treated those in the laboratory under accelerated weathering conditions, the same as we had treated the field stones in the cemeteries. What we were doing was measuring physical and chemical changes. We had our test sites. These are our five cemeteries. Different regions of the US. Each of the climatic regions. The biological growth and the vegetation at the sites did vary widely when we got to the cemeteries. It definitely was needed to look at different areas.

Testing was conducted on both headstones and the sample stones that I mentioned that would weather within the field. Here they were. He stones were matched up. This is a Colorado Yule, so we put a Colorado Yule with it. The next thing was to choose the cleaners. What we were looking for was to choose a wide range of cleaners that had different properties. That worked different ways. In that we eventually chose D2, Daybreak, H2 Orange2 Grout Safe Cleaner, Kodak Photo Flo, and Marble Cleaner Concentrate. You can see the examples here

We also had a very wide range of PH’s. We studied the basic as well. Some … that word … biocides, some that were kelating agents, even one that was slightly acidic. A lot of range of cleaners. Then we began the field trials. Initially what we did was go out to the cemetery, select stones in sunny areas, shady areas, and have them pulled out of the routine maintenance so that these could weather some, start to build up some biological growth, and be taken out of the VA’s regular maintenance schedule for these stones.

We started with photographic documentation. How did they look when we started? what was the initial biological activity? In doing that we actually swabbed each of the stones and sent the swabs back to Harvard Microbiological Center, and they gave us culture counts and types on each of the stones before we started. Then we started with test cleaning patches. This was done in each season. Sorry, twice a year in the fall and the spring at each site. Then we looked at appearance changes and biological regrowth. We’ll talk about each of those.

At the same time we started the lab trials, which was artificial weathering. We also looked at those field studies that we’ve planted. After they had been out in the fields for two years and cleaned for two years with these cleaners, we had them brought back to the lab and we were able to perform tests on those. Laser profilometre , we wanted to see, did the surface change? Did we have loss of surface material? Did we have gain of surface material from salts or that sort of thing? Also some porocity. Did we have one stone that was more coarse then another and did that effect how they were cleaning it?

Lab trials include artificial weathering,laser profilometry, stone porosity, optical microscopy, x-ray fluorescence analysis, and total soluble solids

Lab trials include artificial weathering,laser profilometry, stone porosity, optical microscopy, x-ray fluorescence analysis, and total soluble solids

We also looked at optical, see if we could see salts or changes in the surface. X-ray florescence analysis was also performed. That’s what you see in the photograph here. There again we were looking at any deposition made to the stones by chemicals. We also did total soluble salts testing. Some of these things were non-destructive, some of them were destructive, like the soluble salts. That’s why we had weathered the field samples that then we could cut up test. Also for appearance, we took color measurements with a Minolta cr-400 colorimeter color inhibitor, and what this did was give us a numerical value for color so we could look at direct comparison as far as the color went.

That was done every six months. Also before they were cleaned again to see if there was any visible biological regrowth on that. Also, of course, some other documentation. A lot of photographs of these stones. Each square was photographed with color scale and the entire stone, front, back. Lots of pictures. We also in the field took at portable microscope and photographed all of the stones, each square in the field to look at things like biological regrowth. A lot of times, even though we could see very little, we could take these photographs to see the biological growth that had remained after cleaning or had come back in six months.

One thing that we did find that was of interest to us and also of interest to Harvard’s Microbiological Center was on several of the stones what we found was a very clean appearance, but under magnification, they actually had fungal growth, but it was white. We had managed to kill off a lot of the green and the blacks, but we still had biological growth remaining. It was white, and we hadn’t been able to see that before. For the biological regrowth, these were sent. This is Kristen Pierce at the Microbiological Center at Harvard. What they did was, you can see a stash of our swabs over her shoulder here. Every one of those squares was swabbed in every cemetery every six months, sent back, and the culture counts were recounted and compared to see how the regrowth did in six months.

We also looked at physical changes in the laboratory. I’ll explain the differences between the physical changes that we saw in the field and in the lab. What we did was actually cord and cut samples. Several people had very similar samples. Doctor May was showing was well. Where we took these marble coins, we put them in our QV weatherometer to artificially age them. They ran through eight hundred hours. Every four hours you had UV, every four hours it switches to condensation. At the end of every week, we cleaned them with each of the cleaners, then we rinsed them with the eye water while they were in the condensate cycle. We put them back in, and we let them continue to weather.

Testing for biological regrowth

Testing for biological regrowth

On two of the cleaners, we actually found deposition of salts, but not on the face of the stone, on the back of the stone. X-ray analysis of the front of the stone showed no salt content, but it did of course on the back. What we hadn’t figured on was the possibility of salts being driven and that we couldn’t see with that because the stone was too dense. We found a very fine, very light, fluffy salt on D2 and then a very large, angular crystal on the cleaner Daybreak. We also tried to replicate this in the field, but did not find any salts left at all by D2 in the field samples. I think only one sample ever showed even a minute amount of salt by the Daybreak in the field samples.

After the first year, we had to start eliminating cleaners. We wanted to knock out the ones that we knew just weren’t the tops. One of the things that we did was comparing each of our test methods, one of them being the color measurement. The Delta E is the frequency of change. Anything more than a three is perceivable by the human eye. After about a change of three, we can see a difference. What we looked at was things that had a change of greater than five or greater than ten. By looking at that, Photo Flo showed the greatest number of color changes in both categories. We eliminated Kodak Photo Flo.

That’s not to say that there’s anything wrong with Kodak Photo Flo, but it didn’t have any biocidal properties, so the color change we were seeing was due to biological growth coming back in the stone. We found those negative effects of Kodak Photo Flo. Also we looked at the color measurement in the sunny versus the shady and we really thought we’d see a huge difference in this. What we found was there was actually an equal chance of seeing color change in the sunny or shady areas. It didn’t have a whole lot of difference. I was surprised. As you’ve seen Doctor May’s presentation. He had the same thing. They didn’t find a big difference in sunny or shady. Only relative to the space, the trees, in his study.

We did have a greater chance of seeing a drastic color change in the shady location. That was usually due to the proximity to a tree in those stones that were outliers. One of the things that we did run across is a very drastic color change by the H2 Orange 2 Grout Cleaner, which is a citrus-based cleaner, environmentally friendly. What we found in this was … and this is the square that’s cleaned with that after six months. What you see is most of them retain a very white appearance, but we had a very green appearance. It didn’t necessarily have a higher biological growth count. What it had was it could kill off everything but this very green algae.

If you came back two or three hundred feet, you could see a very green square left. That was definitely a negative impact that the national cemeteries definitely wouldn’t want. The photo gets washed out on the projection with the lights, but it is very green. We also looked at the biological activity. Here we have the shady versus sunny. This is the fungal activity at Jefferson Barracks National Cemetery. Now, the biological activity by location. This is who had the most growth. Of course, Santa Fe National Cemetery had very little. I’m sure no one here’s surprised. Actually, the first time I ever showed up at the cemetery to talk to them, they said, “Oh, this test study sounds like a great idea. Tell you what? We’ll trade you. You give us enough rain to have biological growth, and we’ll clean whatever you want.”

Biological Activity

Biological Activity

We did see a lot of biological growth in Bath, New York and if you’re familiar, this is up in the mountains. About two hours outside of Buffalo into the mountains. You have a heavy fog that sits in there a lot. Same with San Francisco. Of course we have a very humid environment in Alexandria. One of the things that has come out of this study that is a new thing is, as you remember, back we had salts deposits left from D2 in the accelerated weathering, but not in the field studies. Upon reading our interim report, we were contacted independently by representatives from Cathedral Stone and Simple Green and said, “Well, we’re concerned about this. We want to make the best product, so we want to make sure that this is something that we need to know about.”

They actually sent us a new D2, and that is currently as of Sunday, the testing in the artificial weathering was finished. What we were doing with the new D2 is replicating that entire eight hundred hour cycle study that we had done before using the Daybreak again, the D2 again, and the new D2. When it finished, we had no salt deposits on the new D2 at all. We had a very fine amount on the old D2. When I return to Louisiana we’ll do XRF and XRD analysis of those to try to figure out if any was left behind, but as a visual appearance, there was none left.

One thing that has changed, I’ve been informed by the chemist, that it has changed the PH of D2. D2’s PH was at about nine. The new forth of it that they’re showing us has a PH of seven. Evidently, I was told that one of the buffers to get it to nine is what was causing the possible salt problem. It’s been changed and the next phase will then clean some of the field to see if the new cleaner has any different biological activity than the old. I’ve been told that none of that formula was changed at all, so it shouldn’t have any effect. The last phase of the study and as of Wednesday of last week, I talked to Ralph Mitchell of Harvard Microbiological Center. The contracts are in place and we can continue with this new stage. Nick, who presented on the first day was actually who’ll be doing the work.

We have quarried the two types of stone. We have our coupons ready. They will be sent to the Harvard Microbiological Center. They identified the most common forms of algae and fungi that were found in the cemeteries. They incubated those and they will inoculate our stones with the most common funguses and algaes they found. We’ll then clean those. We’ll treat those with the three remaining cleaners, which are D2, Daybreak, and World Environmental Group’s Marble and Granite Cleaner and test the biological regrowth rates of the remaining three cleaners.

The recommendations that we have for the VA at this point are to keep the surface of the stone wet. This is something that wasn’t done. Generally the stones were sprayed dry. Then to apply the cleaner, be it one of these, and after Harvard’s test study we’ll have eliminated it down to the best one for biological regrowth. Agitate if necessary, and then rinse thoroughly with lots of water. That will minimize any of the problems seen. These are a difference in approach than what is currently being done.

To wrap up, the entire report. I don’t know if any of you have seen it, it’s pretty massive. A summary of the first two hundred pages is available at this website or there’s a link through our website for it. I would just like to thank the people that have worked on the project, NCPTT, and especially Sarah Amy Leech of the National Cemetery Administration who spurred this whole project and of course gave the funding for the project. This was through a partnership with both our center and the NCA. She’s been really instrumental in getting a lot of things changed as far as the thoughts of keeping the stones as historical monuments. Also the Microbial and Ecological Laboratory at Harvard University, and Doctor Ralph Mitchell.

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.

National Center for Preservation Technology and Training
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Email: ncptt[at]
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