Florence39 The east doors of the Baptistry Michelangelo called the east doors of the Baptistry the "Gates of Paradise" on account of their beauty. They were commissioned to Lorenzo Ghiberti by the Arte di Calimala or Merchants' Guild, and illustrated from the Old Testament that complete the cycle of human salvation and the omnipotence of God proposed in the first two set of doors. The humanist Leonardo Bruni prepared the iconographic program of the doors in a project consisting of 28 panels, analogous to the two pre-existing sets. For unknown reasons, Ghiberti condensed the program into ten square reliefs, each of which contained more than one episode of the biblical story shown. The contract for the doors was signed on January 2, 1425, and work is known to have begun at the end of 1429. It was finished on April 2, 1452. The workshop, under Lorenzo Ghiberti's direction, included many collaborators. Of note, in addition to his sons Tommaso and Vittorio, were the sculptor Michelozzo, the painter Renozzo Gozzoli and the goldsmith Bartolomeo Cennini. During the flood of 1966 some of the panels were detached from their frame and restoration was immediately begun. Gheberti's original gilding was found to be intact and all restored panels must now be kept in a nitrogen atmosphere to preserve them unaltered. During the lengthy restoration process, the panels were replaced by copies and originals moved to the Duomo Museum (1990).