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 exterior can be seen only from nearby windows and light-wells in the palace. Subsidence and cracking of masonry such as must also have affected the Cappella Maggiore has necessitated the building of very large buttresses to brace the exterior walls. The accretion of other buildings has further altered the exterior appearance of the Chapel. The building is divided into three stories of which the lowest is a very tall basement level with several utilitarian windows and a doorway giving onto the exterior court. Internally, the basement is robustly vaulted to support the chapel. Above is the main space, the Sistine