By Brad Manzenberger
The first thing to understand about cleaning headstones is that not every headstone needs to be cleaned. Before cleaning begins the stone must be assessed to determine 1) that the stone actually needs to be cleaned, and 2) the stone is in sound enough condition to clean it.
When to clean
Reasons to clean a headstone are: readability issues, soiling, staining from iron pins or bronze plaques, effects of pollution, biological growth and vandalism/graffiti. If none of these issue are present, there is no need to clean the stone.
When not to clean
Marble stones often ‘sugar’ as they age. If you run your finger across it you will feel tiny granules, much like sugar. come off the stone. A sugaring stone should not be cleaned. A stone in other stages of decay where cleaning will cause loss of original material or other damage should also not be cleaned.
Document everything. Take photos of the stone as you found it and after you have cleaned it. At a minimum, document in writing all information on the headstone, the condition of the stone as you found it and what methods and chemicals you used to clean it. Copies of this documentation should be given to the person or group responsible for the cemetery. Also consider giving copies to the local genealogy library or history museum.
Materials to avoid
Never use anything metal to clean a headstone. Metal scrapers and wire brushes will typically scratch the stone. Marble and limestone, the most common types of stone in 19th Century Pioneer cemeteries, are relatively soft stone, so the least aggressive methods and tools should be used.
Bleach, acids and common household cleaners should be avoided. While some of these products may you give you the immediate result you want, the long term possibilities are not good. The salts in bleach and cleaners with acid can eat away at the stone as well as cause discoloration. Likewise, common household cleaners contain ingredients that can also cause stone damage and discoloration.
Power tools should not be used. Pressure washing is generally not recommended, but less than 300 psi on a stone in very good condition is sometimes considered acceptable. What comes out of your garden hose with the nozzle is about the most you should use, and even then it depends on the overall condition of the stone. Sandblasting, drills and grinders should be avoided as they typically are too aggressive and remove original material.
Anything else that may cause damage should be avoided. The first rule is always to do no harm.
A product called Wet & Forget has been pushed as a great way to clean headstones and apparently possesses similar properties as the biocides mentioned below. While it may work as advertised in the short term, no long term tests on the effects of this product on historic headstones have been conducted. Therefore, I do not recommend using this product.
Materials to use
In many instances plain water is all that is necessary to clean a headstone. Even when using appropriate chemicals, water is your most important item. You really can’t use too much water in this endeavor.
If plain water is not enough some appropriate materials are non-ionic detergents and biocides. Some non-ionic cleaners that have been used are Kodak Photo-Flo, and Orvus soap. Photo-Flo can be found online or at camera stores that still sell traditional film products. Orvus can be found at farm supply stores.
Biocides are available to clean lichen, mold and other biological growth. Popular brands are BioWash and D2. Both of these products can be used to clean a stone and continue working to ward off new growth after the stone has been cleaned and rinsed.
Other specialty chemicals to remove paint (graffiti), pollution and other less common issues are also available. Always research any product before you use it and make sure to test a small, inconspicuous area before treating an entire marker. Not all problems should be approached by a novice. In more severe cases it is best to consult an experienced conservator.
Metal staining generally requires a poultice to remove the stain. It will not harm the stone other than in appearance.
Keep a one or two gallon pump sprayer (chemical sprayers available at garden supply stores) with plain water to wet the stone before applying chemical and for rinsing on hand. One or two five gallon water jugs may also be handy to ensure you have enough water to complete the job. Small spray bottles can be used to apply the chemical treatment.
Wooden or plastic scrapers can be used gently to remove dirt and thick biological growth before cleaning with a brush.
Soft natural or nylon bristled brushes should be used. Nothing too rigid. Various shapes and sizes are good to have so you are prepared for any nook and cranny.
Once you have determined the stone is in need of cleaning and it is safe to clean (and all before documentation is complete) you are ready to clean. Get the stone wet with plain water and then apply the chemical treatment. Some treatments, such as biocides, suggest a dwell time of two to five minutes. Read the instructions on the label for guidance. Never let a chemical dry on the stone. If it is starting to dry before the desired dwell time reapply a small amount, just enough to keep the stone wet.
Begin scrubbing at the bottom of the stone working up. This helps prevent streaking. Always clean in a circular motion. Keep the stone wet at all times and rinse occasionally while you are cleaning to keep things from being scrubbed deeper into the pores of the stone. Once you are satisfied with your cleaning thoroughly rinse the stone of the chemical. (Although the label on D2 says the product can be left on the stone it is recommended that all chemicals be removed from historic headstones.)
After you have completed cleaning the stone allow a few minutes for the stone to dry and take a final photo. Allowing the stone to dry lightens it slightly and shows the full effect of the cleaning.
The utmost care should be taken when cleaning headstones. Only appropriate cleaning chemicals, tools and methods should be employed. But remember, not every stone needs to be cleaned. Something more than a century old doesn’t need and shouldn’t look brand new.
When in doubt, don’t. It is better to leave a stone as you found it than use an inappropriate treatment and speed up the deterioration process that even a highly experienced conservator can not repair. The stone will not last as a readable grave marker forever, not matter what we do. Only appropriate cleaning and other preservation processes should be used to ensure the longest life possible for the monument.