Cleaning a headstone might sound pretty easy, grab a pressure washer, commercial stone cleaner and go for it, But Wait!!!

You see, that just might be the worst thing you could possibly do to it, next to sandblasting, and to do that to a hundred year old marble or limestone tablet and you would be erasing away history, one detail at a time. The reason that most early headstones, sculptures or heavily carved monuments are made from marble or limestone is that they are a soft stone, making them easy to cut, carve and finish.
Marble and limestone start out being a soft stone, add on a hundred or so years and it becomes fragile, this is due to the loss of minerals from the surface by weathering, organic growth and/or inappropriate cleaning.
These stones are usually so fragile that your can scratch them with your fingernail.
So when it comes to cleaning, using a pressure washer will produce a disastrous result. The high pressure will dislodge the soft minerals on the surface and leave gouges that are destructive to the historical façade and often quite noticeable, in a negative way.
Another thing to know about this “porous crust” on the stone, is that it contains the patina or what some people would call the authentication of age. This discoloration of the minerals on the surface is due to oxidization over a long period of time.
This coloration is the historic patina of the stone and should always be preserved and not removed during the cleaning process. Proper preservation comes down to knowledge, knowledge of history, craftsmanship and materials. like knowing what to use and what not to use, house hold cleaners like bleach, should never be used to clean headstones, it might be fine for the siding on a house, but put it on old white marble and it will react with the stone and cause yellow streaking to appear over time.
Harsh chemicals such as acids should never be used, they bleach out the patina, as well as washes away a micro layer of the historical façade.  
So the question that should always be asked is,   “Will it do any harm”
And the answer should always be “no” it will do no harm,  and if the answer is ever yes, or I don’t know, the process or product should not be used and/or continued.

So, “Bright white” for 100 year old headstones is not the desired result you want to be looking at.

Our goal at Ponsford is to clean away the dirt, debris and organic growth such as fungus, moss and lichen from the stone and leave the clean warm historic glow of an aged monument.

The cleaning of this historic marble sculpture is a time consuming process and is not performed in 10 minute with a pressure washer. But more like 4 -5 days, each area is hand cleaned with soft brushes and biocide and then rinsed with clean water, achieving our goal of retaining the historical patina and integrity of the monument, as well as preserving history.

Cleaning in progress