|This is what happens when elderly parishioners take it upon themselves to restore artwork. This was a 19th century fresco by Spanish painter Elias Garcia Martinez in the Santuario de Misericodia church in Borja, northeastern Spain.|
The technique was originally used to visualize organic pigments in biological samples as a way to screen for skin cancer. Briefly, you use a series of short pulses of light to electrically excite (pump) the sample and then another series of pulses to detect (probe) that change.
The tricky part is finding the proper wavelengths to pump through the apparatus to give you the information you need. Skin pigments are much less variable than the range of materials used to color paintings, and perhaps more importantly, they aren’t combined in myriad ways. However, the scientists were successful in making a nondestructive 3D image of an intact 14th century painting (The Crucifixion by Puccio Capanna).
Left: a femtosecond pump-probe microscope positioned over a section of The Crucifixion by Puccio Capanna.
Top right: a false-color face-on view of the section, showing blue lapis lazuli fragments.
Bottom right: a 60-µm-thick cross-section of the painting, revealing the thickness of the pigment.
PNAS PMID: 24449855.
The authors believe this technique can be used not only to completely deconstruct paintings so that they can be properly restored, but to more fully understand the degradation of pigments so that artwork can be better protected and preserved.