Skip to Content


How Leonardo did it

Alasdair Palmer talks to the French artist who has discovered the secret of the Master’s technique

14 September 2006

9:09 AM

14 September 2006

9:09 AM

Alasdair Palmer talks to the French artist who has discovered the secret of the Master’s technique

How did he do it? Among the many great unanswered questions about Leonardo da Vinci’s ‘Mona Lisa’, that has long been one of the most puzzling. Part of the perennial appeal of the ‘Mona Lisa’, and one reason why, today, there is a perpetual crowd in front of it in the gallery in the Louvre where it sits, protected by thick glass, is that it does not seem possible that the ‘Mona Lisa’ was executed by a human hand. The amazingly fine gradations from dark to light, the completely smooth flesh tones imperceptibly changing so as to create the impression of the contours of the model’s face, seem to be beyond the capabilities of any mere mortal — not to mention, of course, that strange smile.

The techniques Leonardo used in painting the ‘Mona Lisa’ were not understood by his contemporaries, and he seems to have wanted it that way. Leonardo wrote a Treatise on Painting, but he was careful not to give anything away in it: indeed, it seems he deliberately described methods which he did not use, as if to ensure that posterity could never discover the ones he did. His pupils did not employ his techniques after their Master died. There was no school, no workshop turning out ‘Leonardos’ by the dozen. He had no imitators — and no one has ever attempted to forge a work in his late style.

So when Jacques Franck, a French artist and art historian, began working on Leonardo’s technique, he knew he was embarking on a difficult, complicated and long journey. What he didn’t know was how difficult, complicated and long it would be. ‘I first started copying the “Mona Lisa” when I was seven years old,’ he says. Franck is now 60. ‘Of course, I didn’t get really serious about it until I was in my twenties…’ He experimented with various methods. Once he thought he had the right idea about the way Leonardo painted the ‘Mona Lisa’, ‘it took me ten years, working on a single copy, to produce something that looked like the original’.

Jacques Franck’s hunch was that Leonardo built up the ‘Mona Lisa’ by using very thin brushstokes of almost transparent paint, in successive ‘veils’ or layers. ‘Leonardo regarded painting as part of his scientific research,’ Franck explains. ‘He had a very detailed theory of colour, and of how to create the illusion of three dimensions on a flat surface using colour. He did not mix a colour — a flesh tone, say — on his palette first and then apply it. The colour that you see in the face of the “Mona Lisa” is the result of one transparent layer of colour laid over another — which is, of course, the way colour is built up on photographic film. With Leonardo, the process of putting one transparent, or semi-transparent, glaze of colour on top of another is repeated scores, sometimes hundreds, of times. The result, eventually, is the very smooth transitions from one tone to another seen in his late works. It is this which enabled him to capture the contours of the face, to create the effect of the relief that you see in the “Mona Lisa”.’

The technique was not in fact invented by Leonardo: one reason, perhaps, why it actually works. ‘I’ve found it,’ states Franck, ‘in Roman frescos, and certainly in mediaeval and Renaissance ones. Using something like it is essential for creating the impression of, for instance, the contours on a face.’

So what was new about what Leonardo did? And why, then, does the ‘Mona Lisa’ look so different from every other painting? ‘Leonardo’s innovation,’ explains Jacques Franck, ‘was to take “microdivision” to a completely new level: no one had used as many layers as he did, nor such small, indeed tiny, strokes of paint. In the final stages, he must have used single hairs of a brush to apply the paint. I certainly did.’

Using what he believed to be Leonardo’s method, Franck produced copies of the head of the ‘Mona Lisa’, and of ‘The Virgin and Child and St Anne’ (another late work by Leonardo). They are astonishing in their accuracy, and, above all, in the way that they reproduce Leonardo’s uncanny ability to create the smooth flesh tones, and the form of a face apparently shaped only by the way the light falls on it. His copies’ closeness to Leonardo’s originals is the primary evidence that Franck is right: no one working with any other method has ever produced anything as accurate.

In creating them, Franck discovered not only how Leonardo painted, but also why he painted so little, and why he left no school of imitators. ‘It took me ten years to create a picture which exhibits Leonardo’s smooth flesh tones using the “veiling” method of layers of transparent paint. We know that Leonardo took a comparably long time to finish any of his late works.’ The ‘Mona Lisa’, for instance, wasn’t completed for at least a decade after the first sitting. ‘Leonardo was notorious for never finishing his pictures, and I now understand why,’ says Franck. ‘His version of “microdivisionism” is an incredibly laborious and labour-intensive process.’

It would have made no sense economically for an artist trying to make a living by painting to use Leonardo’s method: the length of time involved is totally prohibitive. That’s why none of Leonardo’s pupils — and he had several — followed in his footsteps. It wasn’t simply that he was a greater artist than his pupils. It was that to paint like him would have meant ruin for them: an artist who produced one portrait a decade would, in the 16th century, have starved to death.

That may help to explain why Leonardo did not think of himself as an artist, but as an inventor and scientist. When he offered his services to the princes who employed him, he described his abilities to create machines of war and new technological devices which would enhance the ruler’s power. Only after that did he note that he could also ‘paint a little’.

Franck’s theory of how Leonardo created the ‘Mona Lisa’ was confirmed by tests done on both the ‘Mona Lisa’ and on Franck’s copies: in both cases, infra-red spectrometry and spectrophotometry, along with other techniques for getting at what is beneath the surface of the paint, reveal something very surprising: an astonishing lack of any definite underdrawing. In nearly every other painting from the late-15th or early-16th century, there is a very clear image underneath the painting: the original drawing. But with the ‘Mona Lisa’, as with Franck’s copies, there is just a blur. He was not in the least surprised: ‘That’s exactly what you would expect to find if Leonardo built up the ‘Mona Lisa’ in the way that I build up my copies: by the slow, painstaking accumulation of layers and layers of very thin glaze. With that process, drawing the outline is not the first thing. It’s the last thing.’

Jacques Franck’s theory of ‘how Leonardo did it’ has now been accepted by Leonardo scholars in Italy such as Paolo Galluzzi, professor at the Institute for the History of Science in Florence, and one of the organisers of an exhibition, currently at the Uffizi, entitled The Mind of Leonardo (until 7 January 2007). Jacques Franck’s theory of how Leonardo painted the ‘Mona Lisa’ and his other late works is given appropriate prominence in the Uffizi’s show.

The Louvre has also accepted his account. So it was with surprise that Franck found that the Louvre’s latest scholarly publication on the ‘Mona Lisa’ — Au coeur de la Joconde: Léonard de Vinci décodé — uses his theory, but without mentioning him once. ‘Naturally I was upset. Upset and angry. It took me 30 years to work out how Leonardo painted. Now the Louvre has just stolen the lot.’  

Au coeur de la Joconde was published in France last week. Franck has started legal proceedings against the Louvre for theft of intellectual property. His lawyers say he has an open-and-shut case: the Louvre has already admitted that a ‘mistake’ was made in not crediting him. But that hardly undoes the damage. ‘They need,’ says Franck, ‘to ensure that all copies of the book sold or distributed have something which corrects the “mistake”, and which identifies me as the source of the material on Leonardo’s technique.’

Throughout his life, Leonardo da Vinci was paranoid about having his ideas stolen: that’s why he used mirror-writing and codes, and did not publicise any of his inventions. It is an aspect of the painter into which Jacques Franck feels he now has a special, and very personal, insight.

Alasdair Palmer is public policy editor at the Sunday Telegraph.

Show comments