Brunelleschis Dome by Ross King

Author:Ross King [King, Ross]
Language: eng
Format: epub
Publisher: Walker Books
Published: 2015-07-14T16:00:00+00:00

BRICKS AND MORTAR

DESPITE HIS SUCCESSES in the early years of the dome’s construction, Filippo must have been dogged by the knowledge that once the dome reached a height of 30 braccia, the wardens would meet again to consider whether or not to continue building without centering. Early in 1426, after the second sandstone chain had been swung into place, that moment arrived. The dome had risen to 70 feet above the drum, and the shells, curving inward, had passed the critical angle of 30 degrees, above which friction alone would no longer keep the masonry in place until the mortar cured.

In contrast to the furor when Filippo first floated his plan, in 1426 the debate over whether to continue building the dome without centering appears to have gone smoothly. The capomaestro, now at the height of his powers, carried the day: “We still do not recommend centering,” the amended project reported, citing the difficulties of building the necessary scaffolding. But it remained to be seen whether this feat could successfully be accomplished.

The documents of February 1426 give no more than the merest hint how Filippo’s plan would be implemented. At the same time that it was decided to vault the rest of the dome without centering, another amendment was adopted: in certain parts of the cupola a series of uniquely shaped bricks were to be laid in a special fishbone bond. The twelve-point memorandum of 1420 had decreed that after the two shells reached a height of 24 braccia, either brick or tufa stone should replace sandstone to lighten the load. Brick was ultimately chosen because tufa was not readily available in the vicinity of Florence and so needed to be imported. The Opera therefore contracted for hundreds of thousands of bricks, and Filippo began designing special wooden molds in order to shape them.

The size of bricks was carefully regulated in Florence.

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