Art Your Imagination

The secret of how Leonardo da Vinci produced the optical effects that created the Mona Lisa's enigmatic smile can be revealed for the first time.

Scientists have discovered how the artist managed to achieve his trademark smoky effect, known as sfumato, on the painting; by applying up to 40 layers of extremely thin glaze thought to have been smeared on with his fingers.

The glaze, mixed with subtly different pigments, creates the slight blurring and shadows around the mouth that give the Mona Lisa her barely noticeable smile that seems to disappear when looked at directly.

Using X-rays to study the painting, the researchers were able to see how the layers of glaze and paint had been built up to varying levels on different areas of the face.

With the drying times for the glaze taking months, such effects would have taken years to achieve.

The scientists also suspect that he used his fingers to apply the glaze to his paintings as there are no brush marks or contours visible on the paintings.