Engaged as he was in complex works of engineering and sculpture, it is hard to believe that Andrea Verrocchio was also a master painter – and a very good one at that – but, once again, the documents remove any shadow of doubt and confirm beyond question Vasari’s opinion. In his life of the artist, Vasari described him as an excellent painter, although father of too many sons (not only Leonardo but also Lorenzo di Credi, Botticelli and Perugino all emerged from his workshop). Verrocchio’s influence on the last two is questionable and the subject of continuing and not yet conclusive research. However, no such doubts surround Verrocchio’s artistic paternity of Lorenzo di Credi, and of course of Leonardo. According to his mother Lisa, in 1480 Lorenzo was 21 and a painter in Verrocchio’s workshop on a salary of 12 lire a year. Four years earlier, according to a disturbing document to which we will return later, Leonardo di Ser Piero da Vinci also resided in Verrocchio’s workshop; moreover, he is not mentioned in his father’s tax returns, an indication that he lived in the master’s workshop until at least 1476.
The workshop was very close to the Duomo and had formerly been used by Donatello. Verrocchio rented it because it was more suited to storing the casting equipment that Donatello had previously used for his statues. Other documents tell us that the workshop was also used for the production of paintings even after 1480, when Verrocchio began to work on the monument to Colleoni in Venice, where he eventually moved and then died, in 1487. Verrocchio appointed Lorenzo di Credi as his universal heir, but not without having first provided dowries for his much loved nieces. To Lorenzo, Verrocchio also left a wardrobe of elegant clothes worthy of an affluent merchant, a saddlecloth, a gabanella [mantle, housecoat] of black ciambellotto lined with grey squirrel fur and worn long, in the Venetian style, a doublet lined with fox fur like those featured in many portraits of bankers, other gabbane, and enough fine linen for a good number of chemises. This humble scharpellatore had made good despite his origins, and this passion for expensive garments was perhaps the only luxury that he indulged in. Elegance would also play a role in the education of young Leonardo, for whom it was to become a lifelong idiosyncrasy.
Understanding how an artist could successfully combine such seemingly distant activities as bronze sculpture, the construction of bombards, and the painting of wood panels requires a closer analysis of the practical organization of the Florentine artist’s workshop in the mid-Quattrocento, of which Verrocchio’s is the most refined example.
In a bottega young apprentices like Leonardo were taught how to prepare the materials required for painting and sculpture. They learned the chemical processes needed to create pigments from natural ingredients: for example, they made verdigris by covering a child’s chamber pot with a copper tile and then burying it until the ammonium in the urine corroded and transformed the stability of the copper, turning it a brilliant shade of green, which was excellent for painting the draped mantles of saints. They baked red earth at different temperatures until it turned into red lead and cinnabar; they dried lime until it became the beautiful ‘bianco di San Giovanni’, a special kind of lime white pigment, and they ground carbonized animal bones that had been repeatedly rinsed, producing the bone black used to define the shadows and eyebrows of the enthroned Madonna. They learned to pick up gold leaf and burnish it using a wolf’s incisor, or to mix plaster with glue made by boiling up scraps of skin or the bones of small domestic animals.
They were shown how to smelt iron, too, in order to fabricate razors whose finely honed edge would leave a perfectly smooth surface on the layers of plaster and glue that were applied to wooden panels chosen for their lack of movement after seasoning. The razors were so thin that they would hone the plaster without removing it from the panel, until the mestica, as the plaster mix was known, became as smooth and hard as marble, ready to receive the colour. But before applying the colour they had to learn about the various kinds of bird feathers used to make nibs and the animal fur used to make brushes: pig bristles were too stiff for applying a velatura, or thin glaze – it was better to use instead tufts from a grey squirrel or a foxtail. All this required a detailed knowledge of the natural world, confirming that the real crucible of scientific knowledge in the fifteenth century was the artist’s workshop, all the more so if that artist was not only a painter but also one who cast statues and designed buildings.
The workshop that Leonardo joined offered him a worldly education and taught him the compendium of universal knowledge that had selected itself over centuries. Yet these were not the abstract theoretical systems taught at universities, but rather the tangible knowledge that moved and transformed the world. Extraordinary examples of these compendia or encyclopaedias of art and natural science ante litteram were the codices owned by a number of Florentines from the generation before Leonardo: in particular, Cennino Cennini’s Libro dell’arte (which boasted direct descent from none other than Giotto) and Leon Battista Alberti’s treatise De pictura, which had allowed specialist literature to make significant advances by drawing closer to classical works, above all to those by Pliny and Vitruvius.
All other knowledge was learned and communicated through the daily running of the workshop. In order to make a good brush, one had to know where to source the softest grey squirrel fur, the toughest quills from the hawk, the strongest pig bristles. The same was true of wolf’s teeth, rabbit glue, and the rare lapis lazuli stone that was mined in mountainous areas described by geographers and transported by Arab and Jewish merchants as far as Ferrara, where Florentine artists would go to buy it. After Leonardo had observed nature in all its forms at Vinci, he encountered the next stage in Verrocchio’s workshop: this was nature domesticated, exploited and in part explained with the intellectual instruments of the period. Now his interests could focus on the processes of transformation, something that would never have happened if he had attended a university course at Padua, where students listened to experts speculate in Aristotelian and abstract terms on the formation of the earth and on the multiplicity of the heavens and stars.
At a more advanced stage, the Florentine apprentice learned how to depict space through the geometry of perspective and how vertical lines shrank as they receded in space, while horizontal ones converged towards a vanishing point positioned on an ideal horizon. It was a construction that bordered on intellectual speculation and, as such, had undergone detailed elaboration in the Florentine workshops of many Tuscan architects. In the mid-century, Leon Battista Alberti’s De pictura had also provided a scientific explanation of perspective.
Leonardo also discovered something else in Andrea Verrocchio’s workshop, something that the master himself had invented in order to perfect his drawing skills. Verrocchio used models of human body parts, and it seems very likely that he had started to perform dissections in hospitals in order to study in greater detail how the body worked before drawing it. Hands, torsos and legs, all modelled in clay, were then drawn under different lighting conditions and from different viewpoints in order to achieve a more credible depiction of the object. Verrocchio had also invented, or perhaps simply improved, a completely new way to study how garments would drape over figures. He dipped strips of linen in liquid plaster and then fashioned them into various styles over the wooden and clay models in order to study the hang of the folds and the light that played on them. To improve the drawings, Verrocchio shaded the paper with white, grey or blue pigment before highlighting every nuance in white, until he produced an astonishing degree of realism.
Verrocchio made the most beautiful drawings of the Quattrocento; and Leonardo was well placed to take the level already attained by his master one stage further. For a long period Leonardo’s drawings so closely resembled those of his master that later scholars found it very difficult to distinguish the autograph works of each artist. The woman’s head now in the British Museum, London [Plate 1] amply testifies to the virtuoso degree of realism achieved by Verrocchio using the sfumato effects of light, the composure of the lineaments and the naturalness of the anatomy. What is certain, however, is that his exceptional ability permitted him to oversee all the images produced by his workshop, whether in bronze, stone or paint. Such rigorous control gives a level of uniformity to the output from the workshop and consequently makes it very difficult to identify the work carried out by his collaborators.
His drawings were so complete and detailed that, once transferred to the wooden panel, they could be coloured almost mechanically. Even the shadows were added to the preparatory drawing, in chiaroscuro, before the latter was transferred onto the panel, creating already at that stage a plastic effect, that sculptural relief sought by the master, which his pupils would merely fill in. Having been refined to such an exceptional degree of expressiveness, the drawing was the truly creative phase in Verrocchio’s workshop – and also the controlling instrument that ensured a homogeneous production from the assistants even when the master himself devoted his time to sculpture, which he undoubtedly loved more than any other form of artistic expression.
Vasari prepares the ground for his eulogy of Leonardo by describing how Verrocchio abandoned painting on account of his pupil’s astonishing ability; but today we know for certain that, when Leonardo joined the workshop, Verrocchio was already the greatest sculptor working in Florence. Yet it was Verrocchio’s reputation as an artist that prompted Ser Piero to show him his son’s drawings when the boy arrived in Florence; and the father’s connections with the Medici would certainly have helped him to place Leonardo in Verrocchio’s workshop, which was actively working for Lorenzo and his court in the late 1460s.