Paris, Jul 17: French researchers cracked some secrets of Leonardo da Vinci paintings, including the Mona Lisa, but the world famous smile still remains a mystery.
French scientists analyzed seven Vinci paintings to study the master's use of successive ultra thin layers of paint and glaze, a technique that gave his works their dreamy quality.
Da Vinci painted up to 30 layers of paint on his works to meet his standards of subtlety, claimed the researchers.
Philippe Walter, a researcher said on Friday, Jul 16 that all the layers were less than 40 micrometers, or about half the thickness of a human hair.
Da Vinci's art technique is known as sfumato, which allowed him to give his art the dreamy looks.
The French researchers used a noninvasive technique called X-ray fluorescence spectroscopy to study the paint layers and their chemical composition.
The study also showed that Da Vinci was always engaged in inventing new methods.
In the "Mona Lisa," da Vinci used manganese oxide in his shadings. In others, he used copper. Often he used glazes, but not always.