Thomas Hart Benton was an American painter keenly interested in the revival of old master painting techniques, but acquired his technical information only from translations of Cennino Cennini, remaining unaware of studies by D.V. Thomson and the Fogg Art Laboratory. The consequences are illustrated in the material history of the new school murals, New York City, painted in 1930. The authors describe in detail the techniques used by Benton and the physical consequences of the superimposition of improperly prepared paint layers. Benton himself undertook their restoration in 1931, 1957 and 1968; the most recent restoration (1984), was by the Williamstown Regional Art Conservation Laboratory. During his restorations Benton removed original areas where adhesion was poor; his additions have created even more problems. Benton's claim that the artist had the right to modify his own work, even after purchase by others, is discussed in relation to restoration ethics in general. Photographs. References.