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Our research group has recently designed several products for preserving Cultural Heritage stones with significantly improved performances compared to the commercial products currently in the market. Specifically, some drawbacks of commercial products, such as cracking and poor adhesion to the substrate, have been prevented. Our products are produced by a low- and environmentally friendly cost process; and, of especial relevance, they meet the operational and commercial requirements for application to exterior surfaces of large buildings and structures. The process is so simple that the coatings are produced on the exposed surfaces requiring treatment, under outdoor conditions, using very common deposition methods, such as brushing or spraying. In addition, innovative materials such as superhydrophobic or self-cleaning products, which have been hardly tested on art stoneworks or other Cultural Heritage materials, have been developed.

Many of archaeological sites situated on south of Spain suffer serious deterioration caused by environmental factors, such natural and anthropogenic pollution. In this study we evaluated the effectiveness of a new surfactant-synthesized nanomaterial prepared in our laboratory by mixing silica oligomers and organosiloxane in the presence of the surfactant n-octylamine. The products were evaluated on stone samples from three archaeological sites in the south of Spain. For comparison purposes, two commercial products were also evaluated. The results generated in this study show that the nanomaterial synthesized in our laboratory produces a homogeneous and crack-free coating. In addition, it presents higher hydrophobic and consolidant effectiveness than those associated to the commercial products. Finally, the penetration depth was also higher for our product.

Our research group has recently designed several products for preserving Cultural Heritage stones with significantly improved performances compared to the commercial products currently in the market. Specifically, some drawbacks of commercial products, such as cracking and poor adhesion to the substrate, have been prevented. Our products are produced by a low- and environmentally friendly cost process; and, of especial relevance, they meet the operational and commercial requirements for application to exterior surfaces of large buildings and structures. The process is so simple that the coatings are produced on the exposed surfaces requiring treatment, under outdoor conditions, using very common deposition methods, such as brushing or spraying. In addition, innovative materials such as superhydrophobic or self-cleaning products, which have been hardly tested on art stoneworks or other Cultural Heritage materials, have been developed.

A TiO2–SiO2 nanocomposite material was formed inside the pore structure of a very friable carbonate stone by simple spraying of a sol containing silica oligomers, titania particles and a non-ionic surfactant (n-octylamine). The resulting nanomaterial provides an effective adhesive and crack-free surface layer to the stone, and gives it self-cleaning properties. In addition, it efficiently penetrates into the pores of the stone, significantly improving its mechanical resistance, and is thus capable of converting an extremely friable stone into a building material with self-cleaning properties. Another important advantage of the nanocomposite is that it substantially improves protection against salt crystallization degradation mechanisms. In the trial described, the untreated stone is reduced to a completely powdered material after 3 cycles of NaSO4 crystallization degradation, whereas stone treated with this novel product remains practically unaltered after 30 cycles. For comparison purposes, two commercial products (with consolidant and photocatalytic properties) were also tested, and both alternative materials produced coatings that crack and provide less mechanical resistance to the stone than this product. These results also confirm the valuable role played by n-octylamine in reducing the capillary pressure responsible for consolidant cracking, and in promoting silica polymerization inside the pores of the non-reactive pure carbonate stone.