IL RIVESTIMENTO PLUMBEO DELLE CUPOLE DELLA BASILICA DI SAN MARCO IN VENEZIA

Ettore Vio

Procuratoria di San Marco Venezia San Marco 318 - 30124 Venezia,

ettore.vio@alice.it

ABSTRACT

The cupolas of Saint Marks basilica are unique for their type and elements of construction. They are supported by a timber structure which is over imposed on semi-spherical masonry domes. Originally the cupolas were only constituted by the masonry ones. Later, when the Ducal Palace was extended, they have been raised in order to be visible. Always clad with lead sheets. The technique was introduced in Venice by the proto architects from Byzantium that realized the third basilica of Saint Marks between 1063 and 1094. This ancient technique can still be seen on the Hagia Sophia mosque in Istanbul, built as a basilica in the VI Century. On top of Saint Marks’ cupolas is not a lantern but a little cupola. This paper describes the construction system of the old lead cladding, the aesthetic quality of its surface, and the techniques adopted for the spherical cupola and the swollen, polilobate cupolino. It explains which damages affect the cladding sheeting due to the plastic deformability of the lead, and also to the weather and to the maintenance actions: cracks, punches, cropping. The conservation implies the remodelling of the single piece and the repairing of the damages. The traditional way of soldering with tin does not last long and is not completely compatible with lead. The new technique of TIG soldering makes exclusively use of lead to integrate and reconstitute the missing parts, opening up new perspectives in the conservation of the old sheets.

Key-words: cupolas, lead, failures, conservation, TIG