Laser to reveal famous paintings' secrets

What if you can assess what exactly went into the mind of the renowned artist Leonardo da Vinci while painting the Mona Lisa portrait?

Chemists have unveiled a technique that can get under the skin of paintings to provide a three-dimensional analysis of the old masters' works without causing any damage, says a path-breaking research.

Chemist Warren Warren of Duke University in Durham, North Carolina, and his collaborators adapted an optical-microscopy technique used in medicine for imaging cross-sections of tissue to reveal the structure of paint layers.

This technique discloses which pigments were used and where they sit in the painting, said the study published in the journal Nature.

"This method has been in use in chemical-physics laboratories for half a century, but usually required high-power lasers that would be unacceptable for studying art," said Warren.

Warren teamed up with John Delaney, senior imaging scientist at the National Gallery of Art in Washington DC, and William Brown, chief conservator at the North Carolina Museum of Art (NCMA) in Raleigh.

His team found ways of shaping the laser pulses to make them less intense.

What is more, said Warren, because the method can scan large areas, it can reveal differences in brush-stroke thickness, which might distinguish "features put in place by a master artist from those done by students and apprentices".

"The preliminary results suggest it is a technique with great potential," art-conservation scientist Marika Spring of the National Gallery in London was quoted as saying in the Nature.

"It will be interesting to see how generally applicable it proves, once a wider range of paintings have been tested," she added.

The laser spectroscopy is not the only non-destructive approach for imaging cross-sections of paintings.

X-rays can provide sub-surface imaging, for example, but Warren explains that a strong enough beam requires a synchrotron source, of which there are only a few, highly subscribed facilities in the world.