Dual wavelength excitation for the time-resolved photoluminescence imaging of painted ancient Egyptian objects

Background: The scientific imaging of works of art is crucial for the assessment of the presence and distribution of pigments and other materials on surfaces. It is known that some ancient pigments are luminescent: these include pink red-lakes and the blue and purple pigments Egyptian Blue (CaCuSi4O10), Han blue (BaCuSi4O10) and Han purple (BaCuSi2O6). Indeed, the unique near-infrared luminescence emission of Egyptian blue allows the imaging of its distribution on surfaces.