In the Upper Basilica, reopened in 2000 after intense round-the-clock restoration, Cimabue's works in the apse and left transept have turned black, looking like photo negatives because of the oxidized white lead in his paints, yet you can still feel the intensity of the crowd's anguish in his Crucifixion, blessedly untouched by the earthquake's damaging force.
The white lead in the paint of Cimabue's work has oxidized and turned black.