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 layer of animal glue and "lamp black", all of the wax, and all of the overpainted areas were contamination of one sort or another: smoke deposits, earlier restoration attempts, and painted definition by later restorers in an attempt to enliven the appearance of the work. Based on this decision, according to Arguimbau's critical reading of the restoration data that have been provided, the chemists of the restoration team decided upon a solvent that would effectively strip the ceiling down to its paint-impregnated plaster. After treatment, only that which was painted "buon fresco" would remain. The only reproduction of the Sistine