Fig. 4

FLIM of gradual varnish removal. Rows of images showing the intensity-weighted fractional contributions as they developed during the gradual varnish removal treatment. The representative fluorescence lifetimes and the false-colour scale representing the fractional contributions for each row are shown in the images in the first column. The numbers of solvent applications are indicated in the top-right corners in the first rows of the images in A and B. A The solvent was applied to the painting by a swab without mechanical action. In total, 120 rolls of the swab were performed with 30 rolls between imaging. B The solvent was applied by a swab with mechanical action in a total of 40 rolls with 10 rolls between imaging. Text boxes and arrows in A highlighted the materials of the painting assigned to their characteristic lifetimes. Scale bars 5 mm