Researchers find why ultramarine blue fades

The 20-year restoration of Michelangelo's frescoes on the ceiling of the Sistine Chapel has left visitors in awe of the work's original majesty--notably the brilliance of the blue that graces the Last Judgment's sky. Recent investigations into this shade of blue--ultramarine blue--have brought to light the pigment's tendency to fade. Is it possible that the longevity of such a masterpiece as the Last Judgment could be in peril?