Owing to its unfinished condition, the painting holds the key to the creative world of the artist and his technical processes. A careful study of this interrupted painting helps to provide a plausible basis for that legend that sees the artist as being slow but does not understand the reasons for this slowness. Leonardo is not slow because of his desire to execute the work to perfection. He simply protracts the creative process indefinitely, unlike other artists, who limited the creative phase basically to preparing the drawings. The many preparatory drawings of this painting that have survived, and in particular the two in the Uffizi [Plate 21] and the Louvre [Plate 23], assure us that Leonardo made painstaking preparations for the composition, to the extent of defining details that no other painter worked on in this preparatory phase. However, as we will see, these efforts were in vain because, having transferred the drawing to the panel, Leonardo continued to modify essential parts of the composition, reinventing them and starting a new phase of study, on the painted surface, which for him was critical. This was a phase that could last for years.
The preparatory drawing was transferred onto the plastered panel and then a transparent undercoat [imprimatura] was applied, leaving the drawing visible, so that it could be retraced with a brush dipped in dark colour. Once the drawing was gone over, the edges of a large square were drawn, which the artist used first of all to define the architectural layout. This layout was realized through direct incisions, angles and compass, and with their help the architectural perspective of King David’s palace and the area in front of it were redrawn, as if on a sheet of paper. The cartoon was then transposed onto the lower part using pouncing, together with the principal figures in the group: the Virgin and child, the Magi, and the other figures around them. This first light drawing, consisting of pinpricks of dust, was given greater consistency using a fine line traced in charcoal pencil, which was in turn darkened with a watery brush. Slight adjustments to the folds of garments and to the outlines of limbs and profiles were made during this passage from dust to pencil. These were again altered when the lines were gone over with darker brushstrokes, both wider and more pictorial.
Then, on the basis of a drawing that was already pictorial, the study of shadows commenced, with darker watercolours that gradually defined the interior space of the painting, as happens in a monochrome painting. Leonardo learned this transition in Verrocchio’s workshop, where the shadows were also refined in watercolours to give relief to the image. But here he went much further, slowly defining a perfectly expressive image through shading, in a way that can be done only in monochrome paintings. At the same time, especially in the upper part of the painting, he began a different and more creative phase of recomposing the scene, which he started to people with possible figures in the gaps between the architecture (although not without having first changed it, as can be seen from the steps of the base to the left, between the horses’ heads). Many of these moving ghosts were not drawn on the cartoon but added freehand, during a period of observing and studying the painting that could last for months.
The artist used the panel like an enormous sheet of drawing paper and first outlined some of the figures using very fine lines, probably in charcoal or pencil. Many of these figures would then be covered by others, or by other parts of the composition. The tree in the centre of the painting, for example, covers a figure that was originally drawn in rapid pencil lines. This ‘re-creation’ of the image accounts for those long production times, which sometimes lasted for years, while the artist gradually peopled the painting with figures and decided which would survive in the final version. The same is true of the compositional details, such as individual gestures or limbs.
The process can be seen clearly in the two horses fighting each other (with greater conviction than the two warriors riding them) on the right of the painting, beside the stables. The two horses were first sketched lightly in profile, and then these profiles were changed: the rear hooves of the horse on the right change position completely and its neck and head are defined in two different ways, so much so that in its present state the horse still looks as though it has two heads [Plate 24]. Over time and after careful reflection, Leonardo chose which of these positions would become definitive by adding watercolour to the part that needed to be seen by the viewer and leaving in profile the part that would be covered by a layer of colour and then eliminated. The front hooves of both horses clearly explain the process of development. The front legs were initially drawn in a profile that did not define the succession of layers, and only at a later stage were the legs of the left horse watercoloured, in order to define their respective perspective positions. It was an unusual choice, also with regard to the medium used to define the image: never a clear line, as used by all other Florentine painters of the period, but a soft outline with a brush barely dipped in black. The slow definition of the image was accomplished within the composition as a whole, which took shape gradually but over an extremely long time, because the work was constantly open to changes.
Having defined the key aspects of the composition, Leonardo then concentrated on the light and on steadily darkening the body masses. This, too, was an open process: it is as if Leonardo was not convinced by the study of light displayed in the drawing and wished to re-create it using the original dimensions and placing the figures in real space, just as Verrocchio used to make clay models that he would then drape in fabrics and illuminate with candles or natural light. Leonardo performed the same mental operation by scrutinizing the figures on the panel, in their final sizes, and imagining them in real space. Other artists restricted themselves to finalizing every aspect of the image on the preparatory drawing; and they used fixed and rigid schemes for lighting. The light came from the top-left corner, sculpting faces, bodies and garments in the same way.
Leonardo set all this aside and wanted to compete with nature, re-creating the light without passing through an abstract graphic scheme. This also helps to explain why he never used a distinct line, either in his drawings or in his paintings. That line was an intellectual abstraction, invented over centuries by artists, architects, geographers and anyone who had to represent the universe, while Leonardo wanted to re-create the universe in painting. Day after day, Leonardo defined his figures with the help of a dark colour, which not by chance was referred to in contemporary terminology as umber or as natural earth. In this process it was precisely the umber, the monochrome wash, that was used to select those areas of the painting that were intended to be seen or to vanish.
In this respect it is worth noting the gradual definition of the figure on the far left of the painting, the one holding onto the pillar that supports the arch and looking at the horsemen who arrive from behind. The figure is shown in transparency against the outline of the pillar; but then Leonardo darkened the uncovered profile of the figure, thus creating a credible spatial development of the detail and producing a clear perception of the relief of the man’s body against the pillar. The same happens with every detail.
The light must focus on the Virgin because it highlights her centrality. In order to achieve this, Leonardo started to darken everything around her, the ground, the rocks and the figures, thus creating that luminous and dramatic focus in which the Virgin and the child shine for now with evanescent light. Indeed, during this phase he had already achieved a sublime emotive and formal result, even before applying the colour. Later he would have to maintain the balance of this luminous drama in colour, for which he always used very low tones. But this process had negative consequences for his creativity, because the sensation of having obtained his goal at this phase made him lose interest in the painting and in the monks, in art and in Florence. He was prompted to pursue instead more distant goals. The Adoration of the Magi would remain at this stage for at least two years, until the moment when Leonardo decided to abandon Florence for Milan in 1482.