I mattoni del Brunelleschi. Osservazioni sulla cupola di S. Maria del Fiore

Brunelleschi's bricks. Observations on the dome of Santa Maria del Fiore. The study summarizes the knowledge acquired so far on the structure of Brunelleschi's dome brickwork. First of all, the execution times are correlated with the development of the building, underlining the slow growth of the construction and the great importance of the quality of the mortar in the structure of the Dome. Examining the extrados of the inner and thicker dome, the facing function of the brickwork visible in the passages, performed with high quality bricks and very thin joints, is underlined, and the incompatibility between the latter and the real brickwork of the dome, characterized by common bricks and thick lime mortar joints, is highlighted. The brickwork of the dome intrados, made visible by stripping off the frescoed plaster in four areas during the restoration works, is analysed in detail. The trend of the herringbone brick rows, characterized by slope changes and strong irregularities, and the laying technique of the ‘corda blanda’ rows (catenary curved inclination of the brick beds in between the ribs), by identifying the laying sequence and the size of the bricks, are examined. The latter are related to the documentary acquisitions. The structure of the external dome is analyzed, underlining the particular constructive technique of the shell, executed as the plugging of the frame made by the ribs and the horizontal arches located at the intrados of the dome. It is highlighted that the ‘corda blanda’ laying of the lantern base is only apparent.