Isleworth Mona Lisa
According to Leonardo's early biographer Giorgio Vasari, Leonardo had started to paint "Mona Lisa" in 1503, but "left it unfinished". However, a fully finished painting of a "certain Florentine lady" surfaced again in 1517, shortly before Leonardo's death and in his private possession. The latter painting almost certainly is the one that now hangs in the Louvre. Based on this contradiction, supporters of the authenticity of the "Isleworth Mona Lisa" claim it is the unfinished "Mona Lisa", made at least partially by Leonardo, and the Louvre "Mona Lisa" a later version of it, made by Leonardo for his own use.
Mona Lisa
The first and most extensive recorded cleaning, revarnishing, and touch-up of the "Mona Lisa" was an 1809 wash and revarnishing undertaken by Jean-Marie Hooghstoel, who was responsible for restoration of paintings for the galleries of the Musée Napoléon. The work involved cleaning with spirits, touch-up of colour, and revarnishing the painting. In 1906, Louvre restorer Eugène Denizard performed watercolour retouches on areas of the paint layer disturbed by the crack in the panel. Denizard also retouched the edges of the picture with varnish, to mask areas that had been covered initially by an older frame. In 1913, when the painting was recovered after its theft, Denizard was again called upon to work on the "Mona Lisa". Denizard was directed to clean the picture without solvent, and to lightly touch up several scratches to the painting with watercolour. In 1952, the varnish layer over the background in the painting was evened out. After the second 1956 attack, restorer Jean-Gabriel Goulinat was directed to touch up the damage to "Mona Lisa"s left elbow with watercolour.