Cleaning Headstones

Cleaning Headstones

To clean or not to clean? That is the question.

It is my opinion that, as a whole, the cemetery preservation/restoration community cleans headstones way too much, often cleaning for the sake of cleaning. This is due in part to the fact that proper cleaning can be taught fairly quickly and it is an easy project for volunteers who want to do something but arent comfortable doing resetting and repair work. But there are really only four times I believe a grave marker should be cleaned.

  1. When repairing a broken marker in order to more closely match mortar used for infill.
  2. When soiling, biological growth or other substances prevent all or part of an inscription from being visible.
  3. When soiling, biological growth or other substances are, or are likely to, cause damage to the marker itself.
  4. Less common issues like graffiti, ferrous metal staining, tree sap, etc.

The point of preserving and restoring historic artifacts like grave markers is to perpetuate their existence for as long as possible, knowing full well they wont last forever. They shouldnt look brand new. But they should look cared for without removing the historic fabric of the cemetery.

The first rule in any type of historic preservation is Do No Harm. To that end Stone Revival Historical Preservation has been a leader in research and in the field experimentation to ensure we are always up to date with the Best Practices of the cemetery preservation field. The research is always an ongoing function of Stone Revival Historical Preservation. We follow practices set forth by such organizations as the National Center for Preservation Technology and Training (NCPTT), the Association for Gravestone Studies (AGS), the Chicora Foundation, and through consultations with other well respected conservators around the United States.

It is advised by the vast majority of conservators and every known organization that the use of any sort of power tool for the cleaning of grave markers is not acceptable. Believe it or not there are contractors that think cleaning soft, 19th Century marble headstones that have weathered for a century and a half with tools such as sand blasters, pressure washers and electric drills with a wheel brush attached is acceptable. More about the drill method below.

Also, standard household chemicals should be avoided. There are numerous acceptable masonry cleaners on the market to cover just about any situation an old headstone may face. Bleach is an absolute no-no. It leaves salts behind which can speed up the deterioration process and will discolor the stone over time. Ammonia was once considered acceptable but there are better, and equally affordable, products on the market so ammonia is no longer recommended. Acids should also be avoided.

Stone Revival Historical Preservation primarily uses D/2 Biological Solution with an abundance of water to clean grave markers. Most of the cleaning issues we encounter can be handled with this product. On some occasions more specialized cleaners are needed, such as removing copper or ferrous metal staining. Grave markers are always cleaned by hand using nylon or natural bristled brushes. All chemicals are rinsed from the stone.

Products like D/2 Biological Solution are called biocides. They are designed to kill off biological growth such as lichen and mold. These biocides work over a period of several weeks after treatment and scrubbing. Initial cleaning will generally show some change, but as the product works over time the stone becomes cleaner.

Example 1:

Original Here we have the Veterans marker for Joseph Stubbs at Greenlawn Cemetery in Franklin, IN. This photo was taken July 2010 before cleaning.

1511289_393423064177270_346994233777737159_n The same marker immediately after cleaning.

11144985_393423110843932_1073005752453920708_n And this is how it looked after six months.

In July 2016 I visited the cemetery and examined the marker. For the first time in six years it is starting to show signs of biological growth returning. These results arent typical. Results will vary from stone to stone as many factors contribute to how much, what type and when biological growth takes hold.

Example 2

In this example we see the before, immediately after and two and a half months after cleaning. The orange discoloration in the middle image is from the biocidal cleaner working to kill off biological growth.

Certain contractors have decided to malign D/2 Biological Solution and other chemical treatments claiming they are bad and damage the stone, while ignoring the damage done with their drill and brush method. These contractors are lying both about the chemical treatments and their own methods, as I will point out.

D/2 Biological Solution was part of a six year study conducted by the National Center for Preservation Technology and Training. In this study NCPTT tested a handful of appropriate cleaners to make recommendations to the National Cemetery Administration for the the care of millions of Veterans grave markers within the National Cemetery system. This test was conducted in the field at various locations throughout the United States as well as in NCPTT laboratories. In the lab setting NCPTT was able to speed up the aging/weathering process to study long term effects of these treatments on marble grave markers. NCPTT recommended D/2 and it has become the industry standard. The NCPTT report can be seen here.

Other cleaners such as Orvus will not have the same long term results as we get with D/2. Only biocides offer that feature. Orvus will remove whatever is on the surface.

Stone Revival has several cleaners in our tool box to best address every situation.

There are methods that can get an old headstone looking brand new instantly. However, these methods damage the stone by removing original stone material from the surface. And we dont want them to look brand new.

Sadly, professional contractors, primarily in Indiana and surrounding states, believe that a Nyalox wheel brush on an electric drill is an acceptable practice. I can only guess that the first contractor to use this method thought it was fine because he was using nylon brushes. Never mind the drill is spinning at up to 3500 rpm.
Dico Products, the manufacturer of Nyalox, markets them as a longer lasting alternative to metal wire brushes. They come in various grit. The course 80 grit is used for cleaning followed by a round of polishing with a 120 grit wheel and then a third round with a 240 grit wheel.


With the initial cleaning step and subsequent polishing steps with brushes with ever finer grit a little more of the surface of the stone is removed. The only people that use this method are the contractor who decided it was acceptable for headstones and the many students that have attended his workshops and took his word for it. Not a single preservation organization in the world condones this sort of practice. And the NCPTT, AGS and numerous well known and respected conservators have specifically condemned this practice. Anyone claiming either the NCPTT or the AGS approves of using any sort of power tool to clean a headstone is being dishonest.

Basically, in one photograph, I can prove that Nyalox removes stone material from the surface of the grave marker.

DSC00709 Here you can see stone dust on my fingertips after polishing the stone. Although that seems pretty obvious there are other examples of the damage caused by this method.

10708433_290348134496892_321212238_n In this photo you can see the horizontal and vertical scratches in the surface of the stone highlighted by returning biological growth.

DSC01822 Or a poorly rinsed stone with streaks of stone dust showing on the base?

DSC01810 And here we have stone dust on the grass around the stone after being abraded with a drill.

No matter what they tell you if they are using Nyalox or similar brushes on drills to clean they are absolutely damaging the marker. There is no doubt about it. And to knowingly cause such damage is unethical.

Equally as damaging but less wide spread than the Nyalox is the use of pressure washers. Some will say that using a pressure washer at less than 300 psi is acceptable if the stone is sound. I prefer to err on the side of caution.

The bottom line with cleaning historic grave markers is that 1. there is an actual need to clean and 2. the least aggressive methods should be used. When you start out with an abrasive wheel brush on a drill you are starting with one of the most aggressive methods possible.


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