The key tools we use in reading headstones are the sun and the human eye. Oblique sunlight casts shadows on incised inscriptions allowing patterns to be recognised and words to be read. Patience is rewarded in graveyard recording when that perfect moment arrives and a previously undecipherable inscription is lit up by the sun emerging from behind the clouds. Using a mirror to bounce the sunlight during afternoon recording sessions onto the headstone face gives surprisingly good results.
Rubbing grass, soil, chalk and other foreigh substances onto a stone are all less effective than the use of a torch and mirror and are strongly discouraged. They do not work and they may damage the memorial stone.
(our favourite torch is the Lenser Lens P7 http://www.maplin.co.uk/led-lenser-cree-p7-high-performance-torch-225316)