<P> 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 . </P> <P> Michelangelo painted onto the damp plaster using a wash technique to apply broad areas of colour, then as the surface became drier, he revisited these areas with a more linear approach, adding shade and detail with a variety of brushes . For some textured surfaces, such as facial hair and woodgrain, he used a broad brush with bristles as sparse as a comb . He employed all the finest workshop methods and best innovations, combining them with a diversity of brushwork and breadth of skill far exceeding that of the meticulous Ghirlandaio . </P> <P> The work commenced at the end of the building furthest from the altar, with the latest of the narrative scenes, and progressed towards the altar with the scenes of the Creation . The first three scenes, from the story of Noah, contain a much larger number of small figures than the later panels . This is partly because of the subject matter, which deals with the fate of Humanity, but also because all the figures at that end of the ceiling, including the prophets and Ignudi, are smaller than in the central section . As the scale got larger, Michelangelo's style became broader; the final narrative scene of God in the act of Creation was painted in a single day . </P> <P> The bright colours and broad, cleanly defined outlines make each subject easily visible from the floor . Despite the height of the ceiling, the proportions of the Creation of Adam are such that when standing beneath it, "it appears as if the viewer could simply raise a finger and meet those of God and Adam". Vasari tells us that the ceiling is "unfinished", that its unveiling occurred before it could be reworked with gold leaf and vivid blue lapis lazuli as was customary with frescoes and in order to better link the ceiling with the walls below it which were highlighted with a great deal of gold . But this never took place, in part because Michelangelo was reluctant to set up the scaffolding again, and probably also because the gold and particularly the intense blue would have distracted from his painterly conception . </P>

What is the medium used in the sistine chapel paintings