Michelangelo used the fresco technique to paint the Sistine Chapel ceiling.
In fresco painting, pigments mixed with water are applied to freshly spread wet plaster. As the plaster dries, a chemical reaction binds the colors into the wall, making the image an integral part of the architecture rather than a separate layer sitting on top. Michelangelo worked primarily in buon fresco, the traditional form using wet plaster.
Because the plaster hardens quickly, he had to organize the ceiling into manageable sections called giornate, or day’s work. Each section required careful planning and rapid execution. The curved vault made the project especially demanding, and early plaster work developed mold because it was initially too wet; the mixture was later adjusted.
Watercolor, tempera, and oil paint are distinct media and are not the correct description of the ceiling’s principal method. Michelangelo could add limited details on dry plaster, or a secco, but the ceiling’s defining technique remains fresco. His experience in the workshop of Domenico Ghirlandaio helped prepare him for this enormous mural commission.