Recent conservation of John Singer Sargent’s Triumph of Religion mural cycle (1890-1919) at the Boston Public Library included a significant objects conservation component to treat over 600 relief elements included in the mural design. This paper discusses Sargent’s sculptural materials and techniques and highlights one cleaning treatment demonstrating an intention to balance relief elements with their surrounding murals. Completed in January 2004 by the Straus Center for Conservation, this conservation project provided a unique opportunity to study the artist’s experimental sculptural materials and techniques. On most of the sixteen marouflaged canvases, Sargent applied decorative relief elements to highlight areas of the design, to animate the surface, and to help incorporate the painted murals into the surrounding architecture. Ranging from low relief to near sculpture in-the-round, the relief materials included painted and gilded plaster, papier-mâché, metals, wood, glass, and Lincrusta-Walton (a nineteenth-century wall covering material). Although Sargent was known almost exclusively as a portrait painter prior to creating the murals, it is thought that he did execute these sculptural details himself. Unlike the complex condition of the oil-painted canvases affected by past restorations, the relief elements appeared largely untouched. Structural problems in many of the relief elements revealed the experimental design and inexperience of the artist with sculptural materials. Treatments focused on stabilizing materials and mounting, and removing heavy grime and dust. This large-scale project required a multi-disciplinary approach to stabilize and clean the mixed media compositions, while considering the surrounding architectural ornaments and lighting created by the artist.