Nanotechnology in cultural heritage conservation: nanometric slaked lime saves architectonic and artistic surfaces from decay

The aim of this study was to evaluate the effectiveness of inorganic compatible treatments, based on nanosized particles of calcium hydroxide (slaked lime) dispersed in alcoholic medium, as consolidants for limestones and painted surfaces affected by different kinds of decay. Both in situ and laboratory tests were carried out on carbonatic, low-porosity stones and on frescoes. The re-aggregating effects of the deposited phase were investigated by superficial area analyses (BET) and SEM-EDX; it was also possible to obtain an estimation of the depth of penetration of the product inside the porous matrix by adopting nanoparticles of magnesium hydroxide as markers. Changes in water-interaction properties were evaluated by water absorption capillarity measurements. The consolidating action of the applied material was also pointed out by observations performed in grazing light on treated areas of painted surfaces. All the results converged in individuating these nanometric particles of slaked lime as an innovative, completely compatible, and efficient material for the consolidation of artistic (lime-based wall paintings) and architectural (limestones) surfaces.