National Geographic : 1994 May
master. Black marks remain where he transferred the outline of her face by pouncing charcoal dust through perforations in a preparatory drawing, or cartoon, he had placed on the wet plaster. Michelangelo brushed on his paint in a rich impasto and made many secco alterations after the fresco dried-a technique nota bly different from his work on the ceiling. For the sky he used crushed lapis lazuli, a semipre cious stone, applied in two lay ers. The vivid blue has faded because early restorers abraded the secco layer of pigment when cleaning the fresco - already filthy by the 1560s. Says restorer Maurizio Rossi, "We can do everything except make color grow where it is no longer."