No amount of searching on arson or ruins has brought up a clear answer to this. So: I have the ruins of a stone building which was burned to the ground about a hundred and fifty years ago. It was a manor house, with lots of Very Burnable Things (and people) inside. The material is limestone. In a place with a climate approximately that of West Virginia, how soon could I reasonably say the black charring would be gone? I think the pictures I've seen of places destroyed by Sherman's March were pretty well clean, and I've certainly never seen any fire damage on medieval structures in Europe, but I wanted to check and make sure. Thank you!