Buried metal artefacts gather stories on their surfaces

COINS AND other metal artefacts dug from archaeological sites bear witness to their burial in the form of the patinas of chemicals which accumulate on their surfaces--and different circumstances will result in different sorts of patina. This is particularly true of objects recovered from underwater sediments, for water can contain all sorts of dissolved substances that like to react with bare metals. But, as Gabriel Ingo of the Institute for the Study of Nanostructured Materials, in Rome, descri...