3. The Mona Lisa virtually unveiled

The varnish on the Mona Lisa is highly degraded. It induces a significant yellowing of the painting as a whole, altering the perception of its original colors. Moreover, no analysis of the varnish's composition has been carried out. Sampling was obviously impossible, and the recently developed technique of non-destructive varnish identification by UV fluorescence emission was not operational in 2004. To recover the Mona Lisa's "true" colors, all that remained was virtual de-varnishing, based on the millions of spectra recorded on...