Overpaint removal from easel paintings using an LQS Nd:YAG laser: The first validation study

In this work, laser ablation has been applied for removing overpaint found on the reverse of a signed easelpainting by Giacomo Balla, one of the founding members of the Futurist movement. After unsuccessfulattempts to remove the overpaint layers selectively using organic solvents, a long Q-switched Nd:YAGlaser (1064 nm, 120 ns) ablation was successfully trialled, enabling the planning of complete uncoveringof a hidden artwork by laser treatment. Laser cleaning was accompanied with a thorough characterisationof the original pigments, binders, and overpaint using Raman and FTIR spectroscopy, along withstratigraphic examination combined with optical and ESEM-EDX analysis. In parallel systematicexperimentation on samples simulating the layers to be removed was carried out to interpret the laserremoval processes being exploited and fine-tune the treatment.