THE SECRET TO HER SMILE

PARIS - Researchers using three-dimensional technology to study the "Mona Lisa" say the woman depicted in Leonardo da Vinci's 16th century masterpiece was either pregnant or had recently given birth when she sat for the painting.

That was one of many discoveries found by French and Canadian researchers during one of the most extensive physical examinations ever carried out on the artwork.

"Thanks to laser scanning, we were able to uncover the very fine gauze veil Mona Lisa was wearing on her dress. This was something typical for either soon-to-be or new mothers at the time," Michel Menu, research director of the French Museums' Center for Research and Restoration, said Wednesday on LCI television.

Menu said a number of art historians had suggested that she was pregnant or had just given birth.

Researchers have established that the picture was of Lisa Gherardini, wife of obscure Florentine merchant Francesco del Giocond, and that Leonardo started painting it in 1503.

The name "Mona Lisa" is the equivalent of "Madame Lisa." La Joconde, as the painting is referred to in many countries, is the French version of her married name.

The scan revealed depth resolution so detailed it was possible to see differences in the height around the paint surface cracks and in the thickness of the varnish.

"We now have very precise information about the thickness of the layers," Bruno Mottin, of the French restoration center, told reporters in Ottawa, Canada. "We know how the painting is painted, with very thin layers of painting. That's one of the things we couldn't see by the naked eye, and that Canadian technology brought
us."

John Taylor of Canada's National Research Council said there were no signs of any brush stroke. "That includes the very fine details of the embroidery on the dress, the hair," he said. "This is the 'je ne sais quoi' of Leonardo. The genius. We don't know how he applied it."

The scan even revealed Leonardo's first conception of Mona Lisa.

"The 3-D imaging was able to detect the incised drawing to provide us with da Vinci's general conception for the composition," said Christian Lahanier, head of the documentation department of the French research center.

The artist brought the painting to France in 1517. It has been in the Louvre Museum since 1804.

The data collected in 16 hours of scanning, starting in 2004, took a year to analyze. It shows warping in the poplar panel Leonardo used as his canvas, but the Mona Lisa smile is not threatened.

"We didn't see any sign of paint lifting," Taylor said. "So for a 500-year-old painting, it's very good news. And if they continue to keep it the way they have in an environment-controlled chamber, it could remain like that for a very long time."

Menu said all the secrets behind the enigmatic painting have yet to be revealed, including Leonardo's techniques.

"We particularly want to understand how he painted his shadows, the famous 'fumato' effect," Menu said.