INNOVATIVE APPROACHES FOR THE CONSERVATION OF STONE MATERIALS IN CRITICAL MICROCLIMATIC ENVIRONMENTS: THE USE OF HYDROXIDE NANOPARTICLES

The conservation of stone materials in critical microclimatic environments poses a significant challenge due to the thermo-hygrometric fluctuations that promote salt crystallization, material disintegration, and aesthetic degradation. This study aimed to develop an innovative and sustainable method to address these issues, focusing on the use of barium hydroxide nanoparticles as consolidants for frescos in hypogea. The nanoparticles were synthesised via a hydrothermal process in an autoclave and then they were applied on mock-ups developed to replicate the structural and aesthetic characteristics of medieval frescoes. Tests such as water absorption, vapour permeability, colour stability, and surface cohesion were carried out both before and after treatments, as well as following an artificial ageing to simulate long-term environmental exposure. The nanoparticles were then applied in situ on the frescoes of the complex of Santa Maria della Grotta (Marsala, TP) in an environment characterized by high humidity and poor ventilation. The results showed a significant reduction in water absorption, improved surface cohesion, and minimal alteration of the material's original aesthetic and functional properties. Even after artificial ageing, the treated surfaces maintained their enhanced performance, confirming the durability and stability of the treatment.