Cornell researchers developed a process called X-ray fluorescence imaging to recover faded text on stone by “zapping and mapping” the inscriptions.
The group built a machine that generates X-rays a million times more intense than what the doctor uses to image your bones. An X-ray beam is fired at a stone, scanning back and forth. Atoms on the stone’s surface emit lower-energy fluorescent X-rays, and different wavelength emissions reveal zinc, iron and other elements in the stone.
Historians know that iron chisels were commonly used to inscribe stone, and the letters were usually painted with pigments containing metal oxides and sulfides. So where letters and numbers are no longer visible to the eye, the newfound minerals trace their shapes.