Sistine Chapel ceiling Section reference. Michelangelo wrote a poem describing the arduous conditions under which he worked The overt subject matter of the ceiling is the doctrine of humanity's need for Salvation as offered by God through Jesus. It is a visual metaphor of Humankind's need for a covenant with God. The Old Covenant of the Children of Israel through Moses and the New Covenant through Christ had already been represented around the walls of the chapel. Some experts, including Benjamin Blech and Vatican art historian Enrico Bruschini, have also noted less overt subject matter, which they describe as being "concealed" and "forbidden."
Restoration of the Sistine Chapel frescoes have been predicted by previous restorers. One of the major dangers to the frescoes is automotive exhaust, and they are also vulnerable to the effects of the crowds of tourists that pass through the chapel every day, bringing with them heat, humidity, dust and bacteria (the latter of which can biodegrade paints and pigments). The clean plaster surfaces are more in danger from these destructive elements than they were when they were covered with a layer of smoky wax. Previously, the Sistine Chapel's only ventilation was from its windows in the upper level of the walls. To prevent exhaust fumes