Ornamental Stucco in the Courtyard of the Palazzo Vecchio, Florence, Italy.          The ornamental stucco here was done in 1566 under the direction of Vasari.   The artisans were Pietro Paulo Minocci, Ricciavelli da Volterra, Sabastiano Tadda, and Leonardo Marignalli. It is fortunate that the artisans kept notes of their work, including the precise recipe used for the stucco duro. Vasari studied under Giovanni da Udine and probably learned the formula there. Giovanni da Udine, assistant to Raphael, was present with Raphael during the excavations of Nero's Golden House, requested by Pope Leo X. Inspired by the Roman stucco, tirelessly experimenting and probably aided by the works of Vitruvius, they created stucco duro.