ADVENTURES IN ARCHITECTURE: THE SERIES
Il Duomo: Brunelleschi and the Dome of Santa Maria del Fiore
Episode 10: The Lantern

by Jim Atkins, FAIA, FKIA
Illustrations by Jim Anderson

Summary: In our last episode, the great dome of Santa Maria del Fiore reached substantial completion and was consecrated by Pope Eugenio IV. Our man Filippo Brunelleschi had labored for more than 16 years, solving problems, overcoming material shortages, settling labor disputes—you name it, and Filippo had encountered it and resolved it.

Great celebrations marked the consecration first of the basilica of Santa Maria del Fiore, and, a short time later, of Il Duomo. The greatest masonry dome in existence, which many believed could not be built, now stood completed and in use. Workers removed the ox-hoist and paved the floor of the dome with bricks. The dome interior was finally put in service as a grand part of the worship area. Fabric curtains covered the bare window openings, and lamps were installed. Aside from the windows, of which Ghiberti was now in charge, the only remaining significant piece of architecture remaining to be completed was the lantern.

Join us as the Opera declares a competition for the design and construction of the great lantern that will rest atop the dome. The work to construct the dome was long and difficult, and the result was the greatest masonry dome in existence, but all would not be complete until the lantern shone as the crowning jewel on the dome of Santa Maria del Fiore.

Lanterns were a popular design feature on domes in the Renaissance. The prevailing minds of the day insisted on some type of adornment atop domed structures. Some lanterns were also useful because they enabled ventilation much like a chimney, and, if large enough, could admit light into the area below. Since they were a prominent feature wherever they were used, their design and construction was a subject of great anticipation and debate.

Lanterns had been included on models submitted during the dome competition, and the one prepared by Filippo was no exception. However, that was more than 30 years previous, and those models had not survived over time. It did not matter anyway, because no previous design would have endured the debate and manipulations imposed by the Opera, the powerful guild of merchants overseeing the construction of Santa Maria del Fiore.

The Opera ordered a wooden study model of the lantern in 1432 to finalize the lantern’s size and shape. After much discussion, the wardens decided on an octagonal design with a diameter of 12 braccia [about 24 feet]. Brunelleschi lobbied for a smaller size, and it was reduced first to 10 braccia, and later, even smaller. With the basic program for the model established, in 1436 the Opera called for a competition.

And the winner is …
In addition to Filippo, the field of competitors for the lantern included the rival Ghiberti, a woman (much to the dismay of all the men), a leadbeater (considered a lowly mechanic), and Filippo’s hired carpenter, Antonio di Ciaccheri Manetti. It seems that he had helped Filippo with earlier work, including models and the design for the choir. However, in the lantern competition, he plagiarized many of Filippo’s design elements in his own design. (Wow, just what our man needs at this point in the game, another rival!)

Meanwhile, although Ghiberti had been terminated as a capomaestro and was no longer on the Opera payroll, he nonetheless entered the competition with the intention of winning. He and the Opera were at odds over his late delivery of work on earlier projects. It seems that he had a chronic habit of delivering late and failing to adequately concentrate his workforce; shortcomings obviously as challenging back then as they are today.

The wardens began their evaluation of the submissions on December 31, 1436. Conscious of the chance they would be second-guessed; they consulted many available experts and politically influential citizens. Everyone had an opinion and wanted to be an armchair designer.

In the end, our man Filippo won out again, but with the caveat that he must cool his hot temper and accept a measure of what we will call, “value engineering.” In this case, they were not trying to remove money from the project, but instead they were likely playing architect as many owners are prone to do. Watching your design mutate beyond recognition in the hands of an owner is obviously not a modern concept.

Antonio’s attempt to plagiarize Filippo’s design resulted in the deterioration of their relationship, and their combative behavior quickly rose to the level previously established by Filippo and Lorenzo. In the end, Filippo would not live to see the lantern constructed, and Antonio would win out and be named capomaestro. He would be charged with supervising the lantern construction, and he would infuse many of his own design features into the winning Brunelleschi design.

The lantern
The octagonal lantern rests on a marble base above the uppermost sandstone chain. Its walls include eight buttresses that align with the eight ribs, or spurs, of the cupola. The buttresses provide support to pilasters topped with Corinthian capitals, 30 feet in height, which frame the lantern’s eight windows of the same height. The lantern’s interior contains a dome, over which rises the 23-foot-tall conical shaped roof.

Brunelleschi’s design for the lantern was approved by the Opera on December 31, 1436, and work began the next year. Interestingly, work on the lantern took about twice as long as the dome itself. The cause given was the scarcity of good marble and the complexity of the stone design. However, a more realistic reason may be that there was no Filippo commanding the work and solving the occasional design problems. Brunelleschi died on April 15, 1446, at the age of 69, when the lantern was in the early stages of construction.

The lantern was finally completed on May 30, 1471, when the bronze cross was set on top the brass ball. The 7-foot diameter ball and its gilded cross were constructed to a design by Andrea del Verrocchio. The interior of the ball is accessible from the lantern platform by means of a stairway and a series of ladders through one of the hollow pilasters.

The lantern provided a magnificent crowning element for the great dome. Eugenio Battisti, in his book, Filippo Brunelleschi, has this to say:

“The townscape value of the lantern is almost incalculable. Crowning the greatest height of Florence it dominates the city, and its vast size makes it appear a virtual castle or tower. From its terrace one surveys every corner of the city…”

Florentine skepticism
The stone chosen for the lantern was bianchi marmi, the renowned white marble found in the Apuan Alps surrounding the city of Carrara. The large quarries blot the mountainside, and in the winter, the marble can easily be mistaken for snow.

The marble began arriving in Florence in the summer of 1443, having been shipped by river and over land. This time Filippo had no interest in moving the stone. It had been 15 years since his ill-fated venture into the shipping business with the wreck of his amphibious boat, Il Badalone. His interest in side business ventures had apparently cooled.

The stones ranged in weight up to 5,000 pounds, and the Piazza del Duomo soon began to look like a storage yard with white marble stacked everywhere. Some of the townspeople began to voice their concern about the great weight that would be imposed on the dome. In the end it would total 500 tons.

Filippo assured everyone that the weight would be of no consequence. On the contrary, he said that the lantern would act as a “keystone” where it intersected the eight ribs of the dome, and the structure would actually be made stronger.

Construction
Construction of the lantern proceeded without the great master Filippo, although it was his invention and construction of the unique cranes that made the end result possible. His machines hoisted the great stones to their lofty summit, allowing the stonemasons to apply their trade and produce this profound mantle for the great dome.

Although Filippo was no longer around to direct the work and solve the day-to-day challenges the lantern presented, his legacy of design and invention surpassed his mortality and enabled completion of this magnificent edifice.

Rough times
In the years since its completion, the lantern has not fared entirely well. Although its form is substantial, and its design braces it well for the wind, it has proven susceptible to other elements. In 1492, it was struck by lightning, causing a large block of marble to fall to the floor inside the cupola. It was struck by lightning again in 1601, this time destroying the ball and cross as well as much of the lantern structure.

Earthquakes have visited Santa Maria del Fiore on occasion, causing cracks in the structure. Manual monitoring of the cracks started in 1956, and, in 1988, an electronic measuring system was installed with 160 measuring points. It has been determined that the cracks have a median increase of 5.5mm every century. While this is not considered excessive, it has nonetheless caused concern about long-term conservation of the Basilica.

On close inspection, some distress is visible in the lantern marble, and this is thought to be caused primarily by settlement movement. However, even with its centuries of wear, the climb to the top of Il Duomo remains a magnificent experience, especially for architects with an interest in Renaissance architecture and construction.

We will explore this exciting part of our adventure in episode 12, The Dome Today, when we will walk the 464 steps to the lantern terrace and view the wonderful Florentine panorama. There is no better way to appreciate Brunelleschi and his work fully than to stand on the marble lantern floor with the City of Florence below and the Tuscan breeze caressing your hair.