Brunelleschis Dome (6 page)

W
HEN HE RETURNED
permanently to Florence, probably in 1416 or 1417, Filippo moved back into his childhood home near the cathedral, a good vantage point for a man obsessed with the architectural puzzle presented by the dome to survey its progress. He would have found that much had been accomplished on the cathedral. The tambour, or drum, had been constructed between 1410 and 1413, with walls fourteen feet thick in order to support the weight of the cupola. In 1413 a large new crane had been built to raise materials, and two of the three tribunes of the octagon had been vaulted. The church had also just acquired its new name, Santa Maria del Fiore, “Our Lady of the Flower,” having previously been referred to as Santa Reparata, the name of the older cathedral, which was now completely demolished.

Now in middle age, Filippo was short, bald, and pugnacious looking, with an aquiline nose, thin lips, and a weak chin. His appearance was not helped by his dirty and disheveled clothing. Yet in Florence such an unsightly display was almost a badge of genius, and Filippo was simply the latest in a long and illustrious line of ugly or unkempt artists. The name of the painter Cimabue means “ox head,” and Giotto was so unattractive that Giovanni Boccaccio devoted a tale to his appearance in the
Decameron
, marveling at how “Nature has frequently planted astonishing genius in men of monstrously ugly appearance.” Later, Michelangelo would become legendary for his ugliness, which was partly the result of a broken nose earned in a fracas with the sculptor Pietro Torrigiani. And like both Giotto and Filippo, Michelangelo was indifferent to the state of his dress, often going for months on end without changing his dogskin breeches. In the end, ugly and eccentric artists would become so much the norm that Filippo’s biographer, the painter and architect Giorgio Vasari — himself an uncouth man, with a skin disease and dirty, uncut fingernails — marveled that an artist as talented as Raphael should actually have been physically handsome.

Perhaps unsurprisingly, Filippo was unmarried. But although in Florence bachelorhood was not unusual for a man in his forties, since men married late and generally took much younger women as their brides, Filippo would never marry, and in this abstention from family life he also became part of a long and glorious tradition of artists that included Donatello, Masaccio, Leonardo da Vinci, and Michelangelo. Many Florentine artists and thinkers took a dim view of both marriage and women. Boccaccio, who never married, criticized Dante for having done so, claiming that a wife was a hindrance to study.

No sooner was he settled in Florence than Filippo took steps to become involved in the cupola project. In May 1417 the Opera del Duomo paid him 10 florins for drawing plans of the dome on parchment. What these plans showed is not recorded, but Manetti reports that Filippo’s advice had been eagerly sought by the wardens after his return from Rome. That he should have insinuated his way into the heart of such an important project at this stage is possibly surprising, regardless of his growing reputation as a student of Roman vaulting techniques. Despite his youthful promise as a metalworker he had, at the age of forty-one, accomplished relatively little in practical terms. In 1412 he had given advice on the construction of the cathedral in the nearby town of Prato, but the work being done there was decorative rather than structural, entailing the encrustation of the church’s facade with the dark green stone known as serpentine. And so far he had failed to receive a single architectural commission except for a house near the Mercato Vecchio that he had built for his kinsman Apollonio Lapi.

By 1418 Filippo was probably best known for an experiment in linear perspective. This experiment must have been conducted in or before 1413, when Domenico da Prato refers to him as “the perspective expert, ingenious man, Filippo di Ser Brunellesco, remarkable for skill and fame.” It was one of the first of Filippo’s many innovations and a landmark in the history of painting.

Perspective is the method of representing three-dimensional objects in recession on a two-dimensional surface in order to give the same impression of relative position, size, or distance as the actual objects do when viewed from a particular point. Filippo is generally regarded as its inventor, the one who discovered (or rediscovered) its mathematical laws. For example, he worked out the principle of the vanishing point, which was known to the Greeks and Romans but, like so much other knowledge, had long since been lost. Greek vase paintings and marble reliefs show an understanding of perspective, as do some of the scene paintings for Greek tragedies staged in Athens, including those of Aeschylus. The Roman scientist Pliny the Elder claimed that this method of representation (which he calls
imagines obliquae
,“slanting images”) had been invented by a painter of the sixth century
B.C.
named Kimon of Kleonai. The Romans made use of perspective in their wall paintings, and some of its principles were described by the architect Vitruvius. Furthermore, it seems inconceivable that buildings such as the Pantheon or the Colosseum could have been built without their architects executing perspective drawings of some sort.

After the decline of the Roman Empire, however, the technique of perspective drawing was lost or abandoned. Plato had condemned perspective as a deceit, and the Neoplatonist philosopher Plotinus (
A.D.
205-270) praised the flattened art of the ancient Egyptians for showing figures in their “true” proportions. This prejudice against the “dishonesty” of perspective was adopted in Christian art, with the result that naturalistic space was renounced throughout the Middle Ages. Only in the first decades of the fourteenth century did the ancient methods of perspective reappear when Giotto began using chiaroscuro — a treatment of light and shade — to create realistic three-dimensional effects.

Filippo might have seen examples of ancient perspective painting during his travels through Italy. But he probably worked out the principles of perspective from quite different sources. The procedures for executing his own painting — plotting lines of sight on a plane surface — he could have learned from the surveying techniques he employed while measuring the ruins of Rome.
¹
Perspective drawing is, after all, similar to surveying in that both involve determining the relative positions of three-dimensional objects for the purpose of protracting them on paper or canvas. The practice of measuring and surveying was highly developed by Filippo’s time: his great leap appears to have been an application of its principles and techniques to the art of painting.

Filippo’s experiment consisted of an almost magical optical trick, a trompe l’oeil painting that, in its clever confusion of life and art, prefigured much later experiments with optical devices such as cameras obscura, panoramas, dioramas, and catoptric art. This painting — one of the most famous in the history of art — has long since been lost to the world. Last known to have been in the possession of Lorenzo the Magnificent, it vanished after the occupation of Florence by Charles VIII of France in 1494, when many works of Florentine art were looted. It was clearly described, however, by Antonio Manetti, who claimed to have held it in his hands and attempted the experiment himself.

For the subject of his perspective painting Filippo chose one of Florence’s most familiar sights: the Baptistery of San Giovanni. Positioning himself a short distance inside the middle portal of Santa Maria del Fiore, some 115 feet from the Baptistery, he painted onto a small panel, in perfect perspective, using a geometrically constructed picture plane, everything that was visible through the “frame” of the cathedral’s doorway: the Baptistery and its surrounding streets, including the wafer makers in the Casa della Misericordia and the corner of the sheep market. In place of a painted sky he substituted a piece of burnished silver, a mirror that would reflect the clouds, birds, and changing sunlight of the actual sky. Finally, he drilled a small hole the size of a lentil bean into the vanishing point of the painting, or that central point on the horizon where the receding parallel lines appear to converge.

Diagram of the optical instrument used by Brunelleschi to render the Baptistery in perspective. The painting is on the left, the mirror on the right.

The panel was then ready for demonstration. Standing six feet inside the doorway of Santa Maria del Fiore — on the exact spot, in other words, where Filippo had executed the panel — the observer was to turn the painted side of the panel away from himself and peer through the small aperture. In his other hand he was to hold a mirror, the reflection of which, when the glass was held at arm’s length, showed (in reverse) the painted image of the Baptistery and the Piazza San Giovanni. So lifelike was this reflection that the observer was unable to tell whether the peephole revealed the actual scene that should have been before him — the “real scene” lying beyond the panel — or only a perfect illusion of that reality.

When the competition for the model of the dome was announced in August 1418, Filippo must have jumped at the chance. In June the aged and infirm
capomaestro
Giovanni d’Ambrogio, who had been called back into service from retirement in 1415 following the premature death of his successor, Antonio di Banco, had built a model for the cupola’s scaffolding. But this model cannot have been especially inspiring, as the Opera saw fit to invite other attempts only two months later. With the prize of 200 florins at stake, Filippo and eleven other competitors hopefully submitted their models. The 1367 model was still sacrosanct, of course: the problem at hand was its practical execution.

How to build the invisible supports demanded by the model — the circumferential chains that had been the subject of such debate in 1366-67 — was still a vexed question. Also essential to the project was the resolution of a difficulty not fully considered by Neri and his group: the temporary wooden framework, or “centering,” needed to support the masonry of the dome while the mortar cured. Except in the Near East, where there was a shortage of strong timber, all masonry vaults were (and still are) constructed on wooden frameworks that are supported either by scaffolding or from the ground. In the cases of most small-span arches the process is relatively simple. A timber center is built to the desired profile in order to support the stones composing the arch. This structure has to be both strong enough to bear the weight of the masonry and rigid enough to resist bending under the incremental loading of the blocks of stone. It also has to be easy to remove when the time comes.

It is sometimes possible to build perfectly spherical domes without this sort of centering because each circular layer of masonry forms a self-sustaining horizontal arch. As one of Filippo’s friends, Leon Battista Alberti, explained in his treatise on architecture, “The spherical vault, unique among vaults, does not require centering because it is composed not only of arches but of superimposed rings.” Each stone or brick, that is, forms part of a horizontal as well as a vertical arch and is therefore held in place by the pressures of the surrounding masonry. But the shape of the cupola in Florence, dictated by the 1367 model, was not circular but octagonal and pointed, meaning that the horizontal courses of masonry would not be continuous, as in a circular dome, but broken at each of the eight corners.

Wooden centering supporting an arch.

The construction of a wooden centering for the dome of Santa Maria del Fiore therefore appeared essential. Yet its design presented the wardens with major difficulties, both technical and financial, first and foremost because the centering, like the dome itself, would have to be a structure unprecedented in scale. Innumerable trees had to be found for the required timber. As the competition was being proclaimed, 32 large tree trunks were delivered to the Opera and cut into 900 feet of planks and 135 stripped beams for use in the scaffolding, centering, and loading platform of the south tribune of the cathedral, now ready for vaulting. The cupola, however, was to be much larger than the tribune and would therefore have required, in one estimate, twenty times as much wood, or as many as 700 trees.
²
The Opera owned a number of forests on the slopes of the Apennines, but timber was rivaled only by marble for its expense and the logistical difficulties of its acquisition, being in short supply and, in the absence of hydraulic saws, extremely labor intensive. It was perhaps an omen that the
capomaestro
Antonio di Banco died while on a trip in search of timber supplies with which to build the centering for the dome.