Exploring portable ultrasonic pulse velocity avails in the conservation assessment of plaster sculptures in museum environment

Ultrasonic pulse velocity (UPV) is generally used in Civil Engineering as an in situ and non-destructive methodology to assess the condition of construction materials. Given the fact that non-contemporary sculpture was traditionally made with similar materials – stone, wood, clay or plaster – a hypothesis arose regarding the possible contribution of UPV for the conservation assessment of sculptures with stone-based materials. Plaster is a fragile material, very susceptible to internal and external fractures, alterations and losses. Museum sculptures cannot be moved to a laboratory, due to conservation protocols and therefore portable UPV could, in theory, play an important role in assessing these artistic structures in situ. There are scarce references to such a methodology, and its implementation implied a partnership with Soares dos Reis National Museum (Porto, Portugal) for an experimental approach to three plaster sculptures made by A. Soares dos Reis: “St. Joseph”, “St. Joachim” (both made in 1880) and “Narcissus” (1881). The aim of this study was to assess if portable UPV could help to detect superficial and internal damages and differences between the original plaster and added materials.