CLEANING GRAVESTONES:
Use the Gentlest Means Possible
By Camille Bowman,
Architectural Conservator
It is most often in the spring, usually concurrent with pilgrimages to historic
homes, that the "cemetery bug" bites. Well-meaning individuals and
groups go for a cemetery-cleaning day, armed with chlorine bleach, scrubbing
powders, and sometimes even machine-driven pressure washers. Although it gives
everyone a fine feeling of satisfaction to attack old, darkened markers with
vigor and elbow grease, sometimes, unfortunately, more harm than good is done.
It comes as a big surprise to people who think of masonry
as the most durable of materials to learn that the marble, granite and limestone
of old grave markers is far softer and more porous than one would think. For
this reason, the general rule of thumb in cleaning them is: ‘Use the gentlest
means possible."
When you undertake a cemetery cleaning project you must first determine what you
want in the way of "clean." Remember that old, weathered stone does
not have to look new. You probably want to remove harmful pollutants or lichen,
but you certainly don’t want to scrub until the surface of the stone erodes.
(Or, worse, you would not want to blast the surface of a gravestone until you
can no longer read the inscription!)
Approach each project, no matter what material the grave marker is made of, by
asking yourself, ‘what is the gentlest means possible? The harshest, quickest,
or cheapest method is often not the gentlest. And, certainly, blasting with
chemicals, sand, pecan shells, glass beads, or even water is not the gentlest
means possible. Make test patches of your proposed cleaning technique on an area
of the structure that is least visible. Begin with plain water (at garden hose
pressure) and a soft bristle brush. You will find that some foreign materials
are removed quite satisfactorily with this simple approach-dark algae from a
marble surface, for example.
Should further action be needed, the next step should be the slow and cautious
addition of a mild detergent to the water. However, before any detergent is
added, the stone surface should be thoroughly soaked with water, again at garden
hose pressure. It takes time to thoroughly soak stone-thirty minutes minimum,
and some sources recommend soaking a stone for 24 hours! The reason for the
soaking is to make sure that the detergent is applied only to the surface of the
gravestone; if not thoroughly saturated,
the stone will absorb the detergent, making it impossible to rinse away. It is
very important to understand that acids are very damaging to marble and
limestone, and chlorine bleach (such as Clorox and Purex) is very bad for almost
all stone, including polished granite. Many people have totally lost the
polished face of a fine granite marker by conscientiously scrubbing with
household bleaches. If you feel you need something in addition to a mild
detergent, use a diluted solution of ammonia (1 part ammonia to 3 parts
water). You can also try a photographic solution named Triton X, which is
recommended by conservators as a gentle cleaner. Water and gentle scrubbing
should do the job. Keep in mind that a soft-bristle brush is all that is needed.
Metallic brushes are entirely too harsh, and they also leave particles on the
surface
of the stone that can rust. Always watch carefully to make sure that none of the
stone’s surface is eroding as you scrub.
