Effects induced in marbles by water-repellent compounds: the NMR contribution

The purpose of this paper is to investigate nuclear magnetic resonance (NMR) applications to porous materials widely employed in artistic and historical monuments and largely studied in the Cultural Heritage conservation field, with the aim of studying structural variations induced in the porous matrix by the application of strengthening and water-repellent agents. Carrara marble and Candoglia marble samples, both in the native state and after treatment, were studied and data from relaxation time measurements were compared. Results collected on treated samples are reported and explained in terms of the relation between spin-lattice relaxation time and the structure of the porous materials. Traditional techniques were employed in addition to NMR analysis on marble samples for the evaluation of the preservative performances of three agents generally employed in the restoration yards. Comparative images showing untreated samples with the treated ones were obtained suggesting very useful applications for the determination of treatment effectiveness.