Sistine Chapel ceiling of the Sistine Chapel. At the outset, the plaster, "intonaco", began to grow mold because it was too wet. Michelangelo had to remove it and start again. He then tried a new formula created by one of his assistants, Jacopo l'Indaco, which resisted mold and entered the Italian building tradition. Because he was painting "fresco", the plaster was laid in a new section every day, called a "giornata". At the beginning of each session, the edges would be scraped away and a new area laid down. The edges between "giornate" remain slightly visible; thus, they give a good idea of
Sistine Chapel ceiling "Life of Moses" on the left side. It was carried out by some of the most renowned Renaissance painters: Botticelli, Ghirlandaio, Perugino, Pinturicchio, Signorelli and Cosimo Rosselli. The upper level of the walls contains the windows, between which are painted pairs of illusionistic niches with representations of the first thirty-two popes. A draft by Matteo d'Amelia indicates that the ceiling was painted blue like that of the Arena Chapel and decorated with gold stars, possibly representing the zodiacal constellations. It is probable that, because the chapel was the site of regular meetings and Masses of an elite body of officials