Scientists winkle a secret from the `Mona Lisa’ about how Leonardo painted the masterpiece

Using X-rays to peer into the chemical structure of a tiny speck of the celebrated work of art, scientists have gained new insight into the techniques that Leonardo da Vinci used to paint his groundbreaking portrait of the woman with the exquisitely enigmatic smile. The oil-paint recipe that Leonardo used as his base layer to prepare the panel of poplar wood appears to have been different for the “Mona Lisa," with its own distinctive chemical signature, the team of scientists and art historians in France and Britain discovered. “He was someone who loved to experiment, and each of his paintings is completely different technically,” said Victor Gonzalez, the study's lead author and a chemist at France’s top research body, the CNRS.