Vatican museum experts reveal Michelangelo painting techniques during restoration

Vatican Museum experts finished a major restoration of Michelangelo's "The Last Judgment" fresco in the Sistine Chapel in April.

The project marked the first large-scale restoration of the artwork in over 30 years. Workers spent three months removing a layer of white grime from the fresco, which formed from the dry sweat of millions of visitors over many years.

The museum released a book that provides a chronological record of the work and details new discoveries made by experts during the process. The chapel remained open to the public throughout the three months of cleaning.