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There is a historical building near where I live where the walls are covered in pencil writing. The notes were taken over centuries by multiple generations of the family that lived there. There are all kinds of things-- names, recipes, poems, sketches. (Some are quite historically unique-- for example, a Confederate child's drawing of a fanged, monstrous Abraham Lincoln.)

Several rooms in the house, however, have patches where the wall has been repaired, seemingly just by adding more plaster on top of the previous layer. Words disappear under the patches, leaving sentences unfinished. Clearly, there is more writing underneath. This is mysterious. I want to know what's under there.

Beings that graphite is a material with physical properties varying significantly from plaster, I wonder if there might be some way to image this writing. Graphite is a conductor, it's diamagnetic, acoustically and thermally anisotropic.

Unfortunately, my physics in this area is limited, so I'm not sure where this gets me. Would it show up on an ultrasound? Maybe a thermal camera? Can anyone think of a different scheme?

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  • $\begingroup$ Maybe X-ray scattering techniques ? $\endgroup$ – PM 2Ring May 17 at 5:15
  • $\begingroup$ I suspect that terahertz imaging could do it, but it would not be easy! $\endgroup$ – S. McGrew May 17 at 5:29
  • $\begingroup$ Laser ablation mass spectroscooy could do it for sure, but of course you would need to re-plaster the wall. $\endgroup$ – S. McGrew May 17 at 5:31
  • $\begingroup$ Read The Archimedes Codex for an account of how an ancient book with very faded ink was imaged. Also, I have heard about paper that was gently buried by hot ash in Pompei and burned to charcoal was imaged. It was so fragile that it would crumble at a touch, so it had to be done on site. But I don't know details. Check at a museum. They are sometimes interested in layers of paint on old paintings. $\endgroup$ – mmesser314 May 17 at 5:58

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