Fig. 4

Luminescence lifetime imaging of the cartonage. (Left panel, top) False colour map of the effective PL lifetime reconstructed on details of the Cartonage following 355 nm pulsed laser excitation. The map is superimposed over the UV-induced fluorescence image of the artwork. (Right panel, top) The distribution of lifetime values in the cartonage in pixels (counts) vs. lifetime; the lifetime histogram shows a tri-modal behaviour, suggesting the presence of three different fluorescent materials with effective lifetime values of 3.1, 3.4 and 3.8 ns. (Left panel, bottom) False colour map of the PL lifetime reconstructed on details of the Cartonage following 532 nm pulsed laser excitation. The map is superimposed over the visible-induced NIR-PL image of the artwork, and show the use of Egyptian blue for different details of the cartonage painted in dark colours. (Right panel, bottom) The distribution of lifetime values in the cartonage in pixels (counts) vs. lifetime, showing a unimodal behaviour with a mean lifetime of 119.3 μs (7.7 μs of interquartile range)