Restoration of the Sistine Chapel frescoes smoke and exhaust fumes of the city, being "much dirtier than the ceiling proper". The building was a little unstable and had already shifted considerably prior to Michelangelo's work of 1508, causing cracking of the ceiling, the crack in the "Judith" pendentive being so large that it had to be filled with bricks and mortar before painting. The upper part of the ceiling provided Michelangelo an irregular surface due to cracks and water seepage. Continued ingress of water from the roof and from unroofed exterior walkways above the ceiling level had caused seepage which carried down salts from the building
Sistine Chapel ceiling to a strongly projecting painted cornice that runs right around the ceiling, separating the pictorial areas of the biblical scenes from the figures of Prophets, Sibyls, and Ancestors, who literally and figuratively support the narratives. Ten broad painted crossribs of travertine cross the ceiling and divide it into alternately wide and narrow pictorial spaces, a grid that gives all the figures their defined place. A great number of small figures are integrated with the painted architecture, their purpose apparently purely decorative. These include two faux marble "putti" below the cornice on each rib, each one a male and female pair;