The Mona Lisa is an enigma that has fascinated generations of art lovers. Leonardo da Vinci’s fine technique and use of coloured glazes gives it a wonderful chromatic subtlety, but this process is impossible to recreate, making restoration of this priceless, aging painting very challenging. Not only that, but the layers of varnish added over the years have become intermixed with the pigments and glazes, which means any attempts at removing the varnish may unintentionally alter the painting itself.
Now, with Pascal Cotte’s multispectral camera and detailed computer analysis, we can dig down through the layers of the Mona Lisa without changing the original brushstrokes. We have been able to accurately reproduce the masterpiece, and reveal all the details of its history. For the first time ever, we have the privilege of viewing the Mona Lisa in full, vibrant colour – just as Leonardo intended.
Pigments and Binders:
In the 15th century, a wide variety of pigments for painting were available, produced from natural stones and ores. Several are described in Leonardo’s famous Treatise on Painting. Although ‘recipes’ varied between countries and even between artists, the basic components of the pigments tended to remain consistent. Pigments were usually available as powders, which then needed to be mixed with a binder to form usable paint.
Until the 15th century, eggs were used as a binder in a technique known as ‘tempera’. But for the Mona Lisa, Leonardo used a new oil-based binder from the Netherlands (known then as Holland), thought to have been walnut oil. This new type of binder would revolutionise painting, giving rise to what we now refer to simply as ‘oil paints’.
Lapis Lazuli – More Expensive than Gold:
Lapis lazuli is a precious blue gemstone used in painting since the Middle Ages. It is ground up to form the pigment ultramarine, which was so expensive in Leonardo’s time that painters would usually invoice their clients for it separately or ask them to supply it. It appears that Leonardo had some at his disposal, as the entire sky is made of lapis lazuli. It is a stunning deep blue pigment and makes an important contribution to the character of the Mona Lisa.
Today, only one manufacturer in the world produces lapis lazuli powder as pure as that used by Leonardo da Vinci. It costs approximately U.S. $20,000 per kilogram. Most painters now use a synthetic version of aquamarine, which is chemically identical.
Virtual Varnish Removal:
With multispectral scanning of the Mona Lisa, it was possible to calculate the ‘spectral response curve’ of the varnish for each pixel and subtract it from the overall image. This means that the effect of the varnish on the appearance of each pixel could be isolated and digitally removed, giving us a clean image that represents the Mona Lisa’s original appearance before the varnish was applied. The end result is astonishing.