Mona Lisa had recently given birth to a baby, a team of Canadian and French scientists announced Tuesday, so her mysterious smile may have expressed the weary joy of a mother with a newborn.
Using infrared technology that allowed them to see beneath a layer of varnish, the researchers found that Leonardo da Vinci's model had a gauzy layer over her dress they say was typically worn by pregnant women of the time, or mothers who had recently given birth. The filmy robe was called a guarnello.
Mona Lisa was Lisa Gherardini, the wife of Francesco del Giocondo, a Florentine cloth merchant. Records suggest she wasn't pregnant when she posed for Leonardo, but that the painting was commissioned to celebrate the birth of her third child, says Bruno Mottin, curator in the research department of the Centre de Recherche et de Restauration des Musées de France.
The infant was a boy, says Mr. Mottin, born before Leonardo began painting the Mona Lisa in the early 1500s.
It was second son for the Italian couple. She had also given birth to a girl, her second child, who died as an infant.
For the artist, the Mona Lisa was more than a portrait of woman or a mother. Leonardo was trying to capture life in all its subtleties in the painting, says Mr. Mottin, and never gave it to the cloth merchant who commissioned it.
The researchers say they carried out the most in-depth scientific study ever done on one of the most famous paintings in the world, using a number of high-tech tools, including a three-dimensional laser scanner developed by Canada's National Research Council.
The scientists carried out their work in a laboratory in the basement of the Louvre in Paris. They had to work at night, when the museum was closed.
They found that in addition to a veil that is visible on her head, Mona Lisa was wearing a dark bonnet that can't be seen under the layer of varnish applied long after Leonardo died, Mr. Mottin says.
They found that the artist had changed the position of one of her hands. She had been gripping her chair as if she was about to get up, but the final painting shows one hand folded over the other in a more relaxed pose.
In his book about the painting, British historian Donald Sassoon notes Giorgio Vasari, a biographer of Leonardo, wrote in 1586 that Mona Lisa was entertained by clowns and musicians to make her smile.
But over the years, her smile has come to be seen as enigmatic, and dozens of theories have been put forward to explain it. Some experts said she was pregnant. Others suggested she suffered from facial paralysis, and smiled her particular smile because she had lost her two front teeth.
The findings announced at a press conference in Ottawa yesterday could change the way both art experts and millions of tourists see the painting when they visit the Louvre. If you know what to look for, you can see the gauzy garment that says Mona Lisa had recently had a baby, Mr. Mottin says.
The dark bonnet, however, is much harder to see.
Canadian researchers John Taylor and Francois Blais used their scanner to help the French determine that the painting, done on a poplar panel instead of a canvas, is in good shape and in no risk of degrading under its current storage conditions. They found that the 12-centimetre split, or crack, on the top of the painting probably dates back to the 18th or 19th century and is not getting worse.
The results of the study have been published in a book called Mona Lisa: Inside the Painting. French and German versions are also available.
The scientists also confirmed what art experts have guessed about the technique, known as sfumato, or smoky finish, that Leonardo used to great effect in the Mona Lisa. It was achieved with layer after layer of mixture of oil, varnish and a small amount of pigment, Mr. Mottin says.
But their investigation didn't reveal what kind of tiny strokes he used, or how many layers he applied to give the outlines of her figure and face such a hazy edge, to blur the line between light, shadow and the woman he was immortalizing through his art.
The mystery of how he painted the Mona Lisa remains unsolved, he says.
"That is really a challenge."