As I clean headstones, I usually look for 2 that are very similar. I then clean one of them (treatment) and leave the other one (control) as a sample of what the headstone used to look like.
A "lamb headstone" usually indicates the final resting place of someone who died at a young age. The photos below illustrate the transformation of some infant headstones.
This grave marker of a Revolutionary War veteran is in an unattended cemetery in rural Orange County, NC. It needed and received some TLC.
The marker below is quite tall, and required lots of time and D/2 Biological Cleaner
The Margaret Strayhorn headstone (below) had accumulated years of dust and grime, but was structurally in excellent condition. With some D/2, elbow grease and patience it now looks like new.
The Maplewood Cemetery in Durham, NC has several veteran's gravestones that need some attention. These are in the "Old Section M" portion of the Maplewood Cemetery in Durham.
Below are some samples from March 2022; these are flat stones that had layers of growth and dirt before being cleaned