Florentine painting
In 1508 Pope Julius II succeeded in getting the sculptor Michelangelo to agree to continue the decorative scheme of the Sistine Chapel. The Sistine Chapel ceiling was constructed in such a way that there were twelve sloping pendentives supporting the vault that formed ideal surfaces on which to paint the Twelve Apostles. Michelangelo, who had yielded to the Pope's demands with little grace, soon devised an entirely different scheme, far more complex both in design and in iconography. The scale of the work, which he executed single handed except for manual assistance, was titanic and took nearly five years to complete.
Sistine Chapel ceiling
The entire ceiling is a fresco, which is an ancient method for painting murals that relies upon a chemical reaction between damp lime plaster and water-based pigments to permanently fuse the work into the wall. Michelangelo had been an apprentice in the workshop of Domenico Ghirlandaio, one of the most competent and prolific of Florentine fresco painters, at the time that the latter was employed on a fresco cycle at Santa Maria Novella and whose work was represented on the walls 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 and fresco 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 how the work progressed. It was customary for fresco painters to use a full-sized detailed drawing, a "cartoon", to transfer a design onto a plaster surface—many frescoes show little holes made with a stiletto, outlining the figures. Here Michelangelo broke with convention; once confident the "intonaco" had been well applied, he drew directly onto the ceiling. His energetic sweeping outlines can be seen scraped into some of the surfaces, while on others a grid is evident, indicating that he enlarged directly onto the ceiling from a small drawing.