Add to ORKGEfflorescence and crypto-efflorescence are nearly always present on the decayed masonry and distributed according to the combination of masonry components and to the masonry texture. After an investigation on the most recent floods occurred in Italy, an experimental research started on site on full-scale masonry models, exposed to the environmental agents of Milan. The walls were subjected to decay caused by the crystallization of sodium sulphate coming from the foundations. These walls can actually simulate the state of naturally contaminated walls before a flood. A flood has been simulated for a period of several days, then the walls were left to naturally dry. The aim was to evaluate with ND techniques the rate of drying and the evoluti...