Leonardo was a member of the Arte dei Medici, Speziali e Mercai – the Guild of Doctors, Apothecaries and Mercers. He had his own recipes for making colours, and he listed many of them in his notebooks. That was unusual for a Renaissance painter, but it fits our knowledge of Leonardo the artist-scientist. The master of light and shade was particularly interested in the variety of ways he could mix colour for shadows: ‘Take green [i.e. malachite] and mix it with bitumen, and this will make the shadows darker. And for lighter shades mix green with yellow ochre, and for even lighter green with yellow, and for the highlights pure yellow. Then take green and turmeric together and glaze everything with it … to make a beautiful red take cinnabar or red chalk or burnt ochre for the dark shadows, and for the lighter ones red chalk and vermilion, and for the highlights pure vermilion, and then glaze with fine lake.’
We don’t know how the artist of the Salvator Mundi prepared his palette, but there is a description by Vasari of the way another artist, who was taught in the same studio as Leonardo, did. Lorenzo di Credi and Leonardo were both trained by the Florentine master Andrea Verrocchio, and sometimes worked on the same pictures together. Di Credi, says Vasari, ‘made on his palettes a great number of colour mixtures, so that they went gradually from the lightest tint to the darkest, with exaggerated and truly excessive regularity, so that sometimes he had twenty-five or thirty on his palette, and for each of them, he kept a separate brush’. Such preparation would also have been necessary for the delicate, painstaking and time-consuming manner in which the Salvator Mundi was painted.
Now Leonardo could pick up his brush and begin to paint – should he have had the inclination, of which we cannot be certain. Unlike every other picture Leonardo is widely recognised to have executed after his fame was established, there is no documentary evidence that his hand ever painted the Salvator. That is not in itself an unusual problem for a Renaissance painting. Thousands of artworks before 1700 were unsigned and undated, leaving art historians with thousands of picture-puzzles to solve. The tool of connoisseurship was developed two centuries ago specifically to tackle this problem. But it is a process which art dealers such as Robert Simon and Alex Parish cannot undertake on their own, since however gifted they might be as connoisseurs, they are potentially compromised by commercial motivations. Thus, it was time to call in the experts.
CHAPTER 5
Martin Kemp is a powerful academic, who positions himself a streetwise scholar, resistant to the elitism of the art world, not afraid to defend his corner. When he speaks, the sentences are elegantly formed and the insights – usually about Leonardo – are admirably precise, but the delivery is stern, as if to ward off anyone who might disagree.
Despite all his decades of scholarly study, he tells journalists modestly that he is just in ‘the Leonardo business’, although he has written an autobiographical account of his adventures in it, Living with Leonardo. He professes to be understanding of, even apologetic towards, people who have misunderstood the artist to whom he has dedicated his academic career: ‘It is worth remembering that many of those who have developed untenable Leonardo theories have invested a large amount of time and emotional commitment in their researches,’ he once wrote sympathetically. ‘I have endeavoured to respond in an understanding manner, although I fear I may have been overly abrupt on occasion.’1
Kemp first studied the sciences at Cambridge University before switching to history of art – an early change of course which some of his academic rivals have used against him, but which placed him in a well-nigh perfect position for the study of the ultimate artist-scientist. He taught at various art history departments in Britain and North America before becoming a professor at Oxford in the 1990s. In 1981 his masterwork was published, Leonardo da Vinci: The Marvellous Works of Nature and Man. It slotted seamlessly into over a century of Leonardo historiography by bringing together Leonardo’s scientific studies and his artistic career.
From Giorgio Vasari, the sixteenth-century Florentine author of Lives of the Artists, until the nineteenth-century essayist, novelist, literary theorist and art critic Walter Pater, Leonardo scholars had focused almost entirely on the paintings. That changed in 1883, when the reclusive German Leonardist Jean Paul Richter published meticulous transcriptions of Leonardo’s papers organised according to themes, such as his writings on art, mechanics, anatomy and water, as well as his letters. Richter’s apposite choice of title was The Literary Works of Leonardo da Vinci. In the 1930s Kenneth Clark contributed a useful catalogue of the Leonardo drawings held in the British Royal Collection and a biography, but that was a sideshow compared to the monumental post-war work of Carlo Pedretti, the Italian professor of Leonardo studies at UCLA who taught himself to read Leonardo’s handwriting as a teenager, and who at the height of his fame would arrive for lectures in a helicopter. In Leonardo: A Study in Chronology and Style, published in 1973, Pedretti arranged around seven thousand surviving pages of Leonardo’s twenty-five extant notebooks in a convincing chronological order.
Kemp picked up the baton from Pedretti. He analysed the notebooks and paintings and evolved a coherent and impressively simple model – ‘a common core’, he called it – for Leonardo’s thinking and a narrative for how it developed. For Kemp, Leonardo’s creativity combined observation, intellect, invention (fantasia) and convention (decorum). Leonardo, said Kemp, set out with the purpose of understanding the mathematical and scientific principles that underlay the natural world, anticipating that there must be a common set of laws that applied to all phenomena:
Those authors who have written that Leonardo began by studying things as an artist but increasingly investigated things for their own sakes have missed the point entirely. What should be said is that he increasingly investigated each thing for each other’s sake, for the sake of the whole and for the sake of the inner unity, which he perceived both intuitively and consciously. In moving from church architecture to anatomy, from harmonic proportions to mechanics, he was not leaping erratically from one separate branch to another, like a frenzied squirrel, but climbing up different branches of the same tree.2
Then, at the end of his life, Kemp argued, Leonardo changed his tune. He became convinced that nature was too diverse and mysterious to be grasped, and this was reflected in his stunningly dynamic series of late drawings of floods and tempests.
In the almost four decades since Marvellous Works, Kemp has published a profusion of scholarly articles and catalogue essays about the intersection of science and art in the work of Leonardo and in the broader Renaissance culture. He has also been active in the less austere world of exhibitions and television documentaries, often involving the reconstruction of a working model based on one of Leonardo’s designs. He has plans for a contemporary dance performance, an orchestral recital and a CD of music related to Leonardo, while he works on a new scholarly edition of one of Leonardo’s scientific notebooks, the Leicester Codex, owned by Bill Gates. He is Mr Leonardo. The intellectual has become in part impresario, and scholarship has merged with showmanship, a trend that can be observed across the entire art historical and museological community in recent times.
Martin Kemp had long been an outspoken critic of the methodology of connoisseurship and attributions in art history. In a lecture in The Hague he said, ‘The state of methods and protocols used in attribution is a professional disgrace. Different kinds of evidence, documentation, provenance, surrounding circumstances of contexts