Gradual cleaning of a seventeenth-century polychrome wood sculpture by Er:YAG laser

This paper describes the application of the Er:YAG laser for the cleaning of a 17th-century polychrome wood sculpture which was originally opulently gilded, but had been totally overpainted around the nineteenth century. A series of diagnostic analyses and laser tests have been performed for a comprehensive understanding of the artistic-technique and the state of preservation, and for controlling the laser cleaning. Cross-sections of minute fragments and samples collected by the Er:YAG laser allowed us to understand the complex stratigraphy. PY-GCMS, SEM-EDX, and XRF analyses highlighted the challenge of this cleaning work. It has been considered appropriate to remove gradually the overpaints on the clothing of the Virgin in order to uncover the original gilded portion, although it might be extremely degraded. The Er:YAG laser ablation allowed the selective removal of different layers of multi-colored overpaint and of the thick and resistant past restoration infilling which covered the thin degraded original layers.