Layers of Renaissance paintings uncovered by X-ray fluorescence

The hidden layers of two Renaissance paintings held in The Louvre have been uncovered by the non-destructive technique of confocal micro-X-ray fluorescence. A series of 14 paintings known as the "Famous Men", with a further 14 held in the Ducal Palace of Urbino, Italy, are thought to have been painted by Justus of Ghent. They are painted on thick poplar panels and are known to consist of several layers.

Ina Reiche and colleagues published details of the technique in the Journal of Analytical Atomic Spectrometry, in which they showed that paint layers as thin as 15-20 µm can be distinguished and overpainted sections are easily identified. For instance, red paint was shown to cover a green robe in the painting of Plato and a purple stole worn by Aristotle covered up a red stole beneath.

The technique could be used for "the development of a mobile set-up for non-invasive painting analysis in museums and possibly in situ on archaeological sites."