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
Restoration of the Sistine Chapel frescoes to the Last Judgment. The restoration was unveiled by Pope John Paul II on 8 April 1994. The final stage was the restoration of the wall frescoes, approved in 1994 and unveiled on 11 December 1999. The aims of the conservators were as follows: In 1979 Colalucci undertook a series of experiments to discover the right approach for the restoration of the frescoes of the Sistine Chapel. The investigation began by testing small areas of the wall fresco, "Conflict over the Body of Moses" by Matteo de Lecce, which had similar physical and chemical attributes to the painting techniques employed