Rimozione delle scritte a pennarello dalle superfici in marmo: approccio fisico-chimico

In the present work we report on the systematic study of the removal of sings by felt tip pens from the marble substrates by means of physical (laser) and chemical means. The advantage of combined approach is based on the preliminary removal of the superficial colorant layers by pulsed laser radiation at 532 nm so as to minimize the risk of the further colorant diffusion into the internal stone structure caused by the potentially more efficient solvent-based cleaning that is performed in the second step. The outcome is demonstrated on the removal of three markers (red, blue and black) of two brands (Uniposca, Marker) from unaged marble substrate. The typology of markers was chosen in agreement with the most diffused types of vandal acts by felt tip pens on stone artworks in Florence (Florence cathedral). For the chemical approach two commercially available products indicated for the removal of graffiti were tested Tergent (Geal) e Art-Shield4 (CTS). The cleaning efficiency, for single cleaning step (laser Nd:YAG, chemical products) and when applied in sequence (laser+chemical cleaning), was evaluated by colorimetric measurements and optical microscopy.