Portable NMR for water studies in cultural heritage: from moisture quantitative mapping to non-invasive treatments evaluation

Portable single-sided nuclear magnetic resonance (NMR) was applied to assess moisture distribution and treatment effects in cultural heritage materials using a stray-field NMR-MOUSE instrument. A quantitative, non-destructive methodology for moisture monitoring was developed based on calibrated 1 H NMR signal-amplitude mapping, enabling discrimination between superficial condensation, rising damp, and hygroscopic moisture retention. The approach was tested in two contrasting environments: the Catacombs of St. Callixtus (Rome) and the Oratory of St. Annunziata (Riofreddo). In addition, one-dimensional depth profiling was used to evaluate conservation interventions by measuring proton density and water relaxation properties as a function of depth. The method was applied to assess the effects of cleaning treatments on historic tempera-painted wooden panels and to characterize water transport in starch-based conservation materials. The results demonstrate the versatility of portable NMR as a robust, non-invasive analytical framework capable of translating raw spectroscopic data into actionable diagnostic metrics for preventative conservation strategies.