The Mona Lisa is one of seven da Vinci paintings in the Louvre analyzed by scientists using X-ray fluorescence. (Amel Pain/Associated Press)

Scientists in France believe they've cracked the secret of how Leonardo da Vinci created subtleties in his paintings, including that of the Mona Lisa.

Experts from the Centre for Research and Restoration of the Museums of France analyzed the artist's use of paint and glaze using a non-invasive technique called X-ray fluorescence.

Da Vinci's shading method, called sfumato, is well known. But now scientists have been able to reconstruct his unique style by examining seven of his works at the Louvre Museum in Paris.

"The results obtained in this study help to understand da Vinci's search toward making his art look alive," the study group said in a statement released this week.

Scientists discovered the artist was able to depict life-like tones in the Mona Lisa, providing depth and shadow, by adding dozens of translucent layers of glaze. The layers are less than half the thickness of a human hair

Using their X-ray technique, the scientists discovered da Vinci was always attempting new methods with his paintings. With the Mona Lisa, da Vinci added manganese oxide in the shadings' glaze; in other paintings he experimented with copper.

The other paintings the group examined include Virgin of the Rocks, Saint John the Baptist, Annunciation, Bacchus, Belle Ferronniere, Saint Anne and The Virgin and the Child.

The results of the study are published in the chemistry journal Angewandte Chemie International Edition.

With files from The Associated Press