 He has published extensively on historic painting techniques, as well as in the field of theory and ethics of conservation and restoration.In 1990, he succeeded Josua Bruyn as chair of the Rembrandt Research Project, the team of scholars that is charged with tracking down Rembrandt's works, authenticating them and, when needed, conserving the paintings.As of 2015, the project has published six volumes on Rembrandt's work, the known Rembrandts, and the techniques used by the painter.