While questions have been raised about who may have commissioned the Mona Lisa, the Louvre version of the painting displays certain techniques used by Leonardo, which raise further questions about the date of execution.

Taken together, the accounts of Giorgio Vasari and Agostino Vespucci indicate that Leonardo painted the portrait of Lisa del Giocondo between 1503 and 1506.

However, a certain glazing technique applied on the Louvre version suggests that it was painted at a later date. Leonardo applied a ‘veiled glazing’, an oil painting technique introduced by Flemish primitives, using multiple layers of lightly tinted varnish over the existing painted surface, achieving subtle differences in colour and shading. This helps to create depth and produce that three dimensional, almost magical look of realism. This should not be confused with Leonardo’s trademark paint-based sfumato technique, which creates realism by eliminating hard edges and brushstrokes, though the glaze is also one of the key secrets behind that enigmatic smile. The glazing was a development by Leonardo beyond his sfumato technique.

However this glazing technique was not used in Italy before Da Vinci began developing it in 1508, after his return to Milan. Many renowned experts confirm this technique demonstrates Leonardo’s later style, and date the execution of the Louvre painting which demostrates this technique after 1510.

In addition, recent evidence presented by the Prado Museum concerning the Prado ‘Mona Lisa’ confirms that the Louvre painting was most likely painted during the last years of Leonardo’s life. Indeed, the museum showed that the Prado painting was painted at the same time and the same place as the Louvre one, suggesting that they were both painted during a much shorter period than was once thought.

Taken together with the travel journal of Antonio de Beatis [see pp. 20-25], this strongly suggests that the Louvre painting was executed following Leonardo’s arrival in Rome in 1513. As a result, Vasari and Vespucci described a different Mona Lisa by Leonardo, painted 1503-06 and the only candidate which fits the description and which cannot be ruled out for any reason as that Leonardo work is the ‘Earlier Mona Lisa’.