Barbara H. Berrie is senior conservation scientist and head of the Department of Scientific Research at the National Gallery of Art in Washington, DC. Caroline Fowler is Starr Director of the Research and Academic Program at the Clark Art Institute in Massachusetts. Karin Leonhard is professor of art history at the University of Konstanz in Germany. Ittai Weinryb is associate professor of art history at the Bard Graduate Center in New York City.