We can’t stress enough the damage that can be caused to old soft tombstones and monuments, when harsh chemicals and procedures are applied. We have given you the shortest and simplest means to damage free cleaning under BASIC STANDARDS…Cleaning. That list is quite short. The long list consists of the many bad things that are used and have been used over the years for cleaning. We will try to list as many of these as we can and focus on the most prevalent culprits. We will also give the best explanations science and studies have to offer on this subject. Remember: anything other than what we have as an approved cleaner, will do some degree of damage. It’s merely a matter of what degree of damage. Stone is much like wood when it comes to taking in moisture. Softer stones can be like giant sponges and that is the biggest danger and concern over what to apply on them. Common everyday soaps to harsh chemical will travel deep into the stones and cause damage from the inside out. This is the type of damage that can’t be detected until it’s too late.
Harmful Cleaners and Cleaning Methods
When it comes to tombstone and monument cleaning, the most important thing about any liquid cleaning solution is ph. balance
Bleach is at the top of the list as the number one harmful cleaner most used. Most who use it do because it’s cheap, kills germs and fungi, and it will bleach white a marble stone. Sounds good in theory, but very harmful. The makeup of bleach – The chemical compound formula for sodium hypochlorite is NaOCl. – reaction – Chlorine and sodium hydroxide will produce sodium hypochlorite Cl2 + 2NaOH = NaOCl + NaCl + H2O. Bleach is damaging do its sodium content. The damaging salt deposits left behind in the stone will break down the stones molecular structure from within.
What damage looks like caused by bleach.
Bleach quite often has an accomplice with equally devastating effects, known as a wire brush.
A wire brush will do extreme damage by removing layers of stone. Sometimes removing entire inscriptions. It becomes compounded damage when used with bleach. Please save the wire brush for your next auto body restoration, not your next trip to the cemetery.
ALL typical household cleaners contain some amount of cleaning agent or byproduct such as sodium that will do some degree of damage. These products are best left under the kitchen sink or in the garage where they can be used around the home and on what they were intended for.
Cleaning with power washers is also not recommended. High pressure water has been known to take layers of skin off of a person. If you can strip paint off of a building, you can strip layers of stone off of a grave marker. Many historic stone structures have had their historic mortars and soft bricks damaged with this process. The two key factors here are, the amount of pressure and the softness of the stone. The real damage occurs when overzealous people turn the pressure up on soft stonework.
This process should only be managed by professionals who use it on a limited basis if at all. Many preservationists want nothing to do with it what so ever and others use it sparingly. But since some historical professionals and historical institutions use this technique, it would be disingenuous of us to not try and represent this subject equally. We caution against it because typically there are too many factors involved and too many things can go wrong very easily. This coupled with the factors of equipment and the large water supply needed, most find it not practical.
Professional battlefield park employees clean the hard granite potion of a monument.
Sandblasting on the other hand should never be used as a method of cleaning. The main point of sandblasting is to remove unwanted material to produce a new prep surface. This means historic stone material will be removed to achieve this. Removing historic stone material from the surface will destroy a stones natural protective skin and cause the stone great harm over a short time.
ANY cleaning of a tombstone or monument by mechanical means is devastating to the stone and not recommended. Stone cleaning is meant to be done with the least invasive methods. Mechanical cleaning is the opposite of that. It is very abrasive and extremely invasive.
As we have stated before, stones have a molecular structure and are complex miniature microcosm worlds of nature. And like most things in nature, they change and develop defense mechanisms. When a stone is below ground in a quarry, it has a different molecular quality than one from above ground. A virgin type quality if you will that has not been exposed to both natural and man-made elements. It’s busy being part of the ever changing waxing and waning processes that take place below the earth’s surface. When it is quarried and brought to the surface, it stands bare and naked to the torchers of the world’s atmosphere. And in response to this, it grows a protective skin in an effort to shield itself from these elements
When you use an abrasive means to clean a stone, you strip away this cloak of protection and leave the stone totally defenseless. This is much like cleaning your teeth with a dremel and removing the protective enamel coating.
The white powder around this stone was its protective skin as the picture denotes.
Ken Follett – founding member and first president of the Preservation Trades Network, experts in the field of historic preservation, was asked the following question.
What are some of the harmful effects that result from using high speed rotary nylon wheels on power tools on gravestones?
“I am a solid advocate of D/2 biological solution. That regardless, the technique of treatment of stone surfaces of cultural heritage value. Polishing with Nyalox brushes on a power drill is totally off the charts on an international basis in the world of stone and monument conservation. Likewise, the bad thinking that gravestones need to be, “returned to how they looked originally”. The very first questions needs to be, “Why do this at all? What is the necessity? Where in our culture does this need come from?”
Some of the devastating effects just 3 short years out from a high speed nylon composite wheel for treatment. The stone to the left was very legible prior to this treatment.
A quote from Lynette Strangstad, Author of “A Graveyard Preservation Primer” The premier book on cemetery conservatorship.
“Briefly in my opinion, “polishing” an old gravestone is not appropriate. The entire stone is altered. Some of the surface is removed. And that fragile surface is the very reason most consider the stone valuable. (Though that is only part of the significance) In grinding the surface, that is polishing, one is removing part of the lettering. Three or four such abrasive cleanings over time, say 15 or 20 years, could easily equal the stone loss that would occur naturally in a 100 or more years. It’s good to remember that care for gravestones is not just to satisfy our aesthetic desire in the present; it is to preserve the stone for future generations. D/2 is an effective and responsible cleaning agent when needed”.
People who use this method attack a stone in a series using all three of these wheels. Note the claim to be far superior to wire brushes lasting 10 X as long. These are aggressive tools used in auto body prep work.
Ken Follett and Lynette Strangstad are two of the most knowledgeable and respected people in this field and have years of studies and experience on their side. They are a prime example of the experts CCUS members gain their knowledge from.
The Midwest has been in the grips of a mechanical cleaning craze for roughly the last 10 years. Our CCUS Colorado member Dianne Hartshorn, can attest that it has traveled from Indiana to Colorado. Several Indiana based companies practice this destructive method and one continues to teach it. This has become known as the “Nylon Drill Cleaning” method. This method used to have a much larger stage that it operated from. But due to many voices coming out in opposition, it has declined and moved underground.
People who attend these classes are completely unaware of the damage that is caused by this method. This is very understandable when an individual or company claims to be an expert in this field. This becomes an even greater problem when others perpetuate this situation over and over, and tout it as the greatest thing since baked bread where grave marker cleaning is concerned. This is how urban legends are born.
Dispelling damaging methods like these and shedding light on no harm methods is a big reason we formed the CCUS. One of our goals was to provide you a place to thoroughly vet preservationists and preservation methods. And thus giving you a group of professionals to choose from to teach a class, perform work, or be advised by.