Sorry for being misleading. I am reading an ambiguous ghost story, where there might or not be ghosts. There is said that the ghost has made the marks that are described in the following way: "I moved close to the door again, to run my fingers over the smudge. It left no trace of soot on them, nor any kind of scent, and its surface was quite smooth. The more I studied it, in fact, the more it seemed to me that the mark had the faintest sort of bloom or patina over it... as though it had somehow developed just below the surface of the wood." I think it was done by a human being; the question for me is "how?" that is why I am looking for chemicals that in combination with paint/whatever would make this illusion.