Leonardo’s paintings have left a trail of documents behind them – contracts for commissions, legal filings from irate clients, eyewitness statements from admirers, oral histories recorded by the children of men who knew him, and even notes in the margins of books on completely different subjects. Such documents are a mine of information.
There are legal agreements for many of Leonardo’s commissions, each of which contains its own set of illuminating details about Leonardo’s profession and character. The one for his first major work, the Adoration of the Magi, offered him a piece of land as payment, which he couldn’t sell for three years, while he had to pay for all the paints and gold leaf himself. He was soon behind schedule, and the monks wrote to him telling him to hurry up. Within a year they had given up, writing off the small sum they had already advanced Leonardo so he could buy wheat and wine. Leonardo was a genius, but also temperamental and, by turns, a self-critical perfectionist: he worked slowly and left many works unfinished, much to the exasperation of his clients. A trail of lawsuits followed him wherever he went.
In 1500 another set of angry monks, this time Milanese, from the Confraternity of Immaculate Conception, refused to pay for the Virgin of the Rocks, now in the National Gallery in London, saying it hadn’t been finished. Leonardo countersued, arguing that the previously agreed fee was too low for the quality of work he was providing. The dispute lasted years. In 1506 a judge ruled in favour of the monks, arguing that there was not enough of Leonardo’s hand in the picture, and that he had to return to Florence and finish it. He went back reluctantly, but it is not known what additional work he carried out on the painting.
Another important client, the Council of Florence, was disappointed the same year, when the artist left for Milan leaving behind him the unfinished Battle of Anghiari, now lost. Leonardo had ‘taken a goodly sum of money and provided a small beginning of a great work, which he should have made’, complained the Gonfaloniere, one of the city’s leaders.
Where there are no surviving contracts, we often read of Leonardo’s paintings in the letters and memoirs of awestruck fans, who recorded for posterity the moment they met the great artist. Secretaries and agents of cardinals and countesses left entries in their diaries marvelling at the paintings and notebooks they had seen when they visited his studio, such as Antonio de Beatis who saw the St John, the Mona Lisa and the Virgin and Child with St Anne in Leonardo’s studio in 1517. Leonardo’s unusual working practices were often a talking point. The Italian author Matteo Bandello recorded watching him working on The Last Supper in 1497:
He would arrive early, climb up on to the scaffolding, and set to work. Sometimes he stayed there from dawn to sunset, never once laying down his brush, forgetting to eat and drink, painting without pause. At other times he would go for two, three or four days without touching his brush, but spending several hours a day in front of the work, his arms folded, examining and criticising the figures to himself. I also saw him, driven by some sudden urge, at midday, when the sun was at its height, leaving the Corte Vecchia, where he was working on his marvellous clay horse, to come straight to Santa Maria delle Grazie, without seeking shade, and clamber up on to the scaffolding, pick up a brush, put in one or two strokes, and then go away again.
Proof of Leonardo’s authorship of paintings can come from the most obscure and unpredictable sources. The identity of the Mona Lisa and the date when Leonardo started painting it were both subject to dispute until 2005, when a German scholar came across a note in the margin of a Renaissance volume of letters by the Roman orator Cicero. The marginalia came from Agostino Vespucci, a Florentine civil servant who worked for Machiavelli. A line from Cicero, about how the fabled Roman painter Apelles left parts of his paintings unfinished, reminded Vespucci of Leonardo. Cicero commented, ‘Apelles perfected the head and bust of his Venus with the most elaborate art, but left the rest of her body roughly rendered …’ Vespucci jotted next to the text:
… This is how Leonardo da Vinci does all his paintings, for example the head of Lisa del Giocondo and of Anne, the mother of the Virgin. We will see what he is going to do in the hall of the Great Council, for which he has just reached an agreement with the Gonfaloniere. October 1503
From such a recent, chance discovery, art historians could confirm that Leonardo was painting a version of the Mona Lisa by 1503, earlier than many had previously thought, and that her identity was definitely the Florentine noblewoman Lisa del Giocondo.
Leonardo’s works were the subject of public spectacle as well as private reflection. By 1500 he was a celebrity, whose every move was watched and gossiped about. It was a major event when a new Leonardo was finished and unveiled to the general public, akin to the opening weekend of a blockbuster film today. Vasari wrote that when a new cartoon of St Anne was put on display in Florence for two days in 1501 (incidentally the first show of a single drawing in the history of Western art), ‘it attracted to the room where it was exhibited a crowd of men and women, young and old, who flocked there as if they were attending a great festival, to gaze in amazement at the marvels he had created’.
There are only two Leonardos that were undocumented in his lifetime: the Portrait of a Musician in the Ambrosiana in Milan, which art historians tend to think is by Leonardo’s assistant Giovanni Antonio Boltraffio, and the St Jerome, whose authenticity has never been questioned and for which certain probable references can be found. Both of these paintings were made relatively early in Leonardo’s career. There is no Leonardo painting executed after 1496 which is not remarked in contemporary sources – except, perhaps, one now.
No records from the artist’s lifetime, or for a further hundred years after it, mention Leonardo painting a Salvator Mundi. This is all the more surprising because of the significance of the subject matter. The Christ which Leonardo painted in his Last Supper is the subject of a long anecdote in Vasari’s Lives of the Artists. He relates how Leonardo went to see his client, the Duke of Milan, and provided a progress report on The Last Supper, explaining that he had still not yet painted Christ’s head because ‘he was unwilling to seek a model on earth and unable to presume that his imagination could conceive of the beauty and celestial grace required of divinity incarnate’.
If the greatest artist of his times was painting the greatest subject in Christian art, a Salvator Mundi, one would expect to find it recorded in a note in a monk’s chronicle or a secretary’s letters, at the very least. The absence of such documentation is the first great mystery of the Salvator Mundi. It compels art historians to rely on their ‘superpower’, ‘the eye’, alone. The name of the artist and the date of execution of this painting can only be determined by analysis of the style, technique and motifs of the work, but the result of such a process will always lack the certainty of proof.
Leonardo never dated any of his paintings, but on stylistic and technical grounds, the Salvator Mundi can be placed in the second half of his career, beginning after 1500 and ending with his death in 1519. The preparatory drawings must have been made in the early years of the sixteenth century because they are executed in Leonardo’s softer red chalk style. They are usually dated 1502–10. The painting itself has the intense sfumato shading of the second phase of Leonardo’s work, beginning in the sixteenth century. The walnut wood used for the panel points to a date after 1506, when Leonardo returned to Milan. Walnut was a relatively unusual choice in Renaissance Florence, but was widely used by Milanese painters. It is difficult to be more precise, because Leonardo worked on many of his pictures for a long time, painting them slowly, sometimes on and off over a decade or more, occasionally returning to them after an intermission, often never finishing them. The scientific means of dating a panel painting by analysing the rings in the wood, dendrochronology, cannot be used with walnut, because the rings are too widely spaced to give more than the vaguest indication of epoch.
Whatever the day was when the first brushstrokes were applied to the Salvator Mundi, Leonardo had by then become one of the most celebrated living artists of the Italian Renaissance, alongside Botticelli, Piero della Francesca, Raphael, Michelangelo, Giovanni Bellini, Andrea Mantegna and a dozen others. He had progressed from artistic child prodigy to gifted studio assistant, then a master painter with his own practice