A recent study published in the Journal of the American Chemical Society suggests that Leonardo da Vinci was more experimental with his well-known "Mona Lisa" than previously thought—and was likely the creator of a technique seen in works used a century later.

A team of scientists in France and Britain has detected a rare mineral compound（矿物化合物）, plumbonacrite, within the piece. Plumbonacrite forms when lead oxides（铅氧化物）combine with oil. Mixing these two substances is the technique that later artists like Rembrandt used to help the paint dry, according to the study.

Detecting the rare compound in the "Mona Lisa" suggested that Leonardo could have been the original user of this approach, said Gilles Wallez, an author of the study. "Everything that comes from Leonardo is very interesting, because he had lots of ideas, and he was an experimenter, attempting to improve the knowledge of his time," Wallez said. "Each time you discovered something in his processes, you discovered that he was clearly ahead of his time."

The "Mona Lisa", like many other paintings from the 16th century, was created on a piece of wood that required a thick base layer. The researchers believed that Leonardo had made his mixture of lead oxide powder with linseed oil to produce the thick coat of paint needed for the first layer, while unknowingly creating the rare compound.

Nowadays, researchers aren't allowed to take samples from the masterpiece, which resides at the Louvre in Paris and is protected behind glass. Using a microsample that had been taken from an area of the artwork just behind the frame, however, scientists were able to analyze the paint by using a high-tech machine. "These samples have a very high cultural value," Wallez said. "You can't afford to take big samples on a painting."