Search Results (2)

Nanolimes have been commercially available for over a decade as a remineralization agent for natural stone to combat deterioration. While they have been applied successfully and studied extensively, their penetration abilities in different materials have not yet been readily quantifiable in situ and in real time. Using two transparent pore-imitating test systems (acrylic glass (PMMA) and polydimethylsiloxane (PDMS)) and light microscopy, the penetration coefficients (PCs) of two nanolimes (CaLoSiL (CLS) and Nanorestore Plus (NRP)), as well as their solvents, were determined experimentally in square channels of about 100 µm diameter. Their PCs and those for a previously published glass–resin-based test system were also predicted based on measurable material parameters or literature values using the Lucas–Washburn equation. Additionally, a liquid mineral precursor (LMP) of calcium carbonate based on complex coacervation (CC) was investigated as an alternative to the solid particle dispersions of nanolime. In general, the dispersions behaved like their pure solvents. Overall, trends could be reasonably well predicted with both literature and experimentally determined properties using the Lucas–Washburn equation. In absolute terms, the prediction of observed infiltration behavior was satisfactory for alcohols and nanolimes but deviated substantially for water and the aqueous LMP. The commercially available PMMA chips and newly designed PDMS devices were mostly superior to the previously published glass–resin-based test system, except for the long-term monitoring of material deposition. Lastly, the transfer of results from these investigated systems to a different, nontransparent mineral, calcite, yielded similar PC values independently of the original data when used as the basis for the conversion (all PC types and all material/liquid combinations except aqueous solutions in PDMS devices). This knowledge can be used to improve the targeted design of tailor-made remineralization treatments for different application cases by guiding solvent choice, and to reduce destructive sampling by providing a micromodel for pretesting, if transferability to real stone samples proves demonstrable in the future. Full article

Consolidation of mural paintings in hypogea is challenging because of their severe microclimatic conditions, characterized by high humidity levels, low air circulation, the presence of salts efflorescence, and the detrimental growth of biodeteriogen agents. Traditional consolidant products show significant drawbacks when used in hypogeum. Organic compounds, such as acrylic emulsions, are bio-receptive and some inorganic consolidants, such as silica-based products, show a lack of compatibility with the original substrate, which could lead to a reduction in permeability and an increase in the mechanical resistance of the external layer. The presence of solvents in their formulations, particularly short-chain alcohols that can activate germination of fungal spores, leads to the release of great amounts of volatile organic compounds, which are particularly harmful in the hypogeic environment. To solve these problems, restorers of the Istituto Centrale per il Restauro (ICR) decided to use a new aqueous nanolime dispersion, NANOLAQ, consisting of pure and crystalline Ca(OH)₂ nanoparticles dispersed in water, produced by an innovative and sustainable patented procedure. After laboratory testing, the product has been applied on site, on a medieval mural painting in the Ss. Peter and Paul hypogeum in the UNESCO site of Matera (Italy), monitoring the performance in terms of cohesion of the paint layer and preservation of aesthetic features. Full article