The Most Important Facts about Brunelleschi’s Dome

Cathedral in Florence
View on Brunelleschi’s dome

What is the first thing that amazes the travellers who see Florence for the first time? No doubt – it is the dome of the Florentine cathedral, the most recognizable monument of the city, the symbol of its power and beauty. The history of its construction is one of the most fascinating and mysterious stories narrated by the stones of Florence. Considering that a dome of this dimensions was technically impossible to construct at that time, the successful accomplishment of Brunelleschi’s project may seem a real miracle. But let us start from the beginning.

The history of Brunelleschi’s Dome

The construction of a new cathedral began in Florence around 1294 or 1295 but the initial project did not immediately took in consideration the construction of a dome. In fact, at that time nobody would immediately worry about the overall project of the building under construction. The raising of the cathedral started from the façade and from the walls of the main nave, thus the necessity of designing a dome would present itself a bit later. So why should have they worried about it from the beginning?

However, the base of the tambour which would support the dome was ready already in 1315 and this is when the problems started. The space, which was supposed to be covered by the dome was enormous. The tambour was 13 m tall and it arrived 55 meters above the ground level while its external diameter was of 54,8 m and the internal one measured 45,5 m. During the fourteenth century, to construct a dome or a vault the architects would use special wooden armatures, called “centering” which would hold the bricks on the right place until the mortar was dry. It was impossible to apply such a technique for the construction of a dome 34 meters high which arrives at 116 meters from the ground level. It was impossible to find such high trees, necessary for the construction of the centering.

Giorgio Vasari in his Lives of the Most Excellent Painters, Sculptors and Architects recalls different ideas taken into consideration when looking for the solutions for this giant construction. One of them was to fill in the space of the church with dirt mixed with coins and to use it as the support for the dome and the workers. When the dome was ready, the city council would ask the pour inhabitants of the city to clean the church and to take the dirt out keeping the coins that they would found in it. Cleaver enough? Obviously, it was not a solution.

In 1418 the Opera del Duomo, enterprise which organized the construction of the church, announced the competition for the project of the dome. Filippo Brunelleschi and Lorenzo Ghiberti, his long-time rival, they both took part in it. We have to remember that 17 years earlier Ghiberti won against Brunelleschi the competition for the project of one of the Baptistery doors. Brunelleschi, who already at that time started to seek inspiration in Classical sculpture and considered himself the most innovative artist in Florence, felt truly offended by the decision of the committee. After the defeat he left Florence for Rome together with his friend Donatello where they both continued their studies of Classical art, sculpture and architecture.

View on the Dome and the Bell Tower, Florence
View on the dome from the roof terrace of the Rinascente shopping mall

The competition of 1418

In 1418 Brunelleschi was back in Florence convinced more than ever that he was the only one able to solve the problem of the dome. Unfortunately, the committee did not decide the winner of the competition and in consequence both, Brunelleschi and Ghiberti, had to lead the construction of the dome together. For Brunelleschi that was too much. After few discussions with Ghiberti he decided to prove the importance of his knowledge and abilities for the success of the project. Thus, he pretended to be sick and did not show up at work for few days. His absence created a great confusion among the workers and it became obvious that without him the project could not go on. Ghiberti was discharged and Brunelleschi became officially the head master. He promoted his project and in 1436 the dome was finished until the base of the lantern. On 1st August 1436 it was blessed by the pope Eugene IV.

The years of the construction of the dome accelerated the technological development of Florence and its handicrafts. But why is the dome so particular?

The secrets of Brunelleschi’s Dome

Thanks to his technical skills, creativity and collaboration with the Florentine carpenters and blacksmiths, Brunelleschi invented mobile scaffolding which was attached to the already built part of the dome and moved up together with the construction. In order to hoist the bricks from the ground floor Brunelleschi projected a crane, a complex hoisting machinery, which helped the workers to get all the materials they needed directly on the level of the scaffolding. The innovation in the field of cranes, mobile platforms and scaffolding would be subsequently applied not only to architecture but also to the Florentine stage design. In fact, various hoisting machineries would be used during the religious spectacles in the Florentine churches and used to carry the actors from the level of the stage to the heavens located under the roof.

The dome is constructed of two domes, an internal and an external one connected through the intermediary ribs. In order to guarantee the solidity and stability of the dome, Brunelleschi used the fish-bone brick laying technique and introduced the radial-vertical brickwork. There are still few hypotheses, which try to explain Brunelleschi’s technique and we do not know for sure what the architect really did and why. It seems, however, that the workers disposed the bricks using a system of strings attached to the ring on the base of the dome. The cords indicated the exact position and inclination of each brick and allowed the workers to move on. The rotation of the bricks makes the dome particularly resistant to compression and tension, the “pull” and “push” forces as well as to the lateral thrust provoked by the loading, called “hoop stress”.  The lantern which crowns the dome functions as a sort of a tap and keeps in balance the pull and push forces created by the internal and the external domes.

The view on the dome from the Boboli Gardens
The view on the dome from the Boboli Gardens

Brunelleschi managed to complete his ambitious project thanks to his great mental openness and collaborative character. To obtain the mathematical calculations for the dome, he collaborated with Paolo dal Pozzo Toscanelli, an important Florentine mathematician, trained in Padua and active in Florence. To construct the scaffolding and the hoisting machinery, he worked together with the Florentine blacksmiths and carpenters, highly specialized workers who, however, belonged to the lower guilds and, thus, to the lower strata of the society. In fact, this open character of the fifteenth-century Florence, the tendency to build bridges between people of various social background: academics, artisans, rich merchants and humanists, seems to form the background for the creativity and innovation, which exploded in Florence between 1400 and 1500. This is why Brunelleschi’s dome is a perfect symbol of the prosperity of the city and its arts at that time and tell us a lot about the importance of the dialogue between different professional and intellectual environments. We can still learn a lot from the stones of Florence.

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