NMR depth profiles as a non-invasive analytical tool to probe the penetration depth of hydrophobic treatments and inhomogeneities in treated porous stones.

Hydrophobic treatment is one of the most important interventions usually carried out in the conservation of stone artifacts and monuments. The analytical study reported in this paper was aimed at answering general questions such as the penetration depth of a hydrophobic treatment into a porous material, its capability to impair the water absorption, how the presence of a treatment may change the open porosity available to the water, and how a treatment may affect the diffusion of water inside a porous structure. Also, inhomogeneities in treated stones due to sharp variations of the amount of the absorbed product in the porous material were evidenced and scaled.