For years the OHCA, along with other gravestone preservation groups, has recommended not cleaning marble gravestones.  But, no matter how much we admonish folks not to do so, every year we hear about cemetery "clean ups" and learn that some well meaning group has gone out with household bleach or power washers to make the old graveyard "look good."  We also remember the very nice cemetery operator who said, "You conservation people are always telling us what not to do, but you never let us know the right way to do things."

With all of that said, the purpose of this article is to teach you some safer methods for cleaning marble gravestones.  Note that I said "safer" rather than safe.  No matter what cleaning method you use, you will be causing some damage to the stone.  Please read all of the directions before you begin any cleaning project.

Get permission

Contrary to popular opinion, not everyone wants gravestones to be cleaned.  Contact the owner of the cemetery and, if possible, descendants of the deceased before you clean a gravestone.  In most cases cemeteries do not own the markers, so attempting to locate family is recommended even if cemetery owners give permission.

How's the weather?

The primary ingredient of ANY cleaning project is water.  Therefore, do not attempt to clean gravestones on hot sunny days.  Fall and Spring are by far the best times of year for gravestone cleaning, because the biological growth will be soft and easily removed, the stone will not dry out and stain while you are working, and you'll stay cooler and more comfortable as you work.  Rainy days are good for cleaning, but heavy downpours can wash away your cleaning solutions.  Never clean (or be outside) during a thunderstorm. 

Selecting a stone that is suitable for cleaning

Some old grave markers are just too far gone or too delicate to clean under any circumstances.  There are various grades of marble, and poor grades may have a "melted" look as minerals have been washed away by rain.  Others will feel "sugary" when you run your hand over them indicating that the structure of the stone has deteriorated.  Still others will have noticeable cracks or amateur repairs that could be easily expanded or break with the slightest pressure from a scrub brush.  Avoid cleaning any of these stones.

A stone that can be cleaned with relative safety is one that is sturdy and solid, has no noticeable surface deterioration, and has no (or only minor) surface cracks.

 
Sturdy, but covered with grime, the Burkhart monument at Lebanon Pioneer Cemetery is a good candidate for cleaning.

Removal of heavy biological growth

If the gravestone is heavily covered with moss or lichen, there is only one safe method for removing it.  Do not try to remove dried-on biological growth, and do not apply any chemicals or gardening products as they will cause serious damage.  During the rainy season, on a rainy day, take a lot of water with you and go to the cemetery.  If your timing is right, with a gloved hand or soft wet cloth you will be able to gently wipe away the water-saturated moss and/or lichen.  If necessary, remove growth from the carving with a soft-bristled brush or toothbrush.  Wipe the surface with a wet cloth and thoroughly rinse the stone with water.

Cleaning the stone (removing surface dirt)

Your tools should be a bucket, sponges and/or rags, and soft bristle brushes of various sizes.  If you are in doubt about whether the bristles of your brush are soft enough, decide if you would use them to wash the paint on your car; if they would scratch your car paint, they are too stiff for marble gravestones.

Your cleaning agent should be lots and lots of water.  It is acceptable, if necessary, to add a small amount of household ammonia or non-ionic soap (such as Joy dishwashing liquid) to the cleaning water, but it will need to be rinsed off thoroughly with plain water.

Before cleaning a gravestone, all heavy biological growth will need to have been removed (see above).  If you are working on a large or multiple-sided monument, clean one side at a time.

Begin the cleaning process by thoroughly wetting the entire stone or surface on which you are starting.  Dipping a large brush into your water or cleaning solution, begin gently scrubbing the surface from the bottom up; do NOT clean from the top down as you will end up with streaks.  As you work your way up the stone, be certain that the surface remains quite wet; rinse the stone or reapply fresh water frequently if you notice any drying or dirty streaks.  Rinse the stone thoroughly when the entire surface has been scrubbed.

After the initial cleaning, use smaller brushes such as toothbrushes to clean lettering and artwork.  Be certain that the stone surface remains wet during cleaning and that you rinse the stone with plain water following the cleaning.

Safely bleaching marble

The OHCA no longer recommends cleaning any gravestone with any chemical.

Plain water and lots of it are needed before, during, and after.

Some final thoughts before you clean a marble gravestone

The most important things to remember about cleaning marble stones:

	Don’t.
	If you must clean a marble gravestone, the best cleaning product is plain water -- and lots of it.
	Never use anything harder than a soft-bristled brush.  Wire brushes or power washers are NEVER acceptable.
	Never use household bleach or other household cleaning products.
	Everything you take off (except particles of stone) will return.  The dirt, algae, mildew, and biological growth are the result of climactic conditions, and they cause far less damage to the stone than the cleaning you are contemplating.  When you're done and gone, they'll be back.