Application of TiO2 Based Coatings on Stone Surface of Interest in the Field of Cultural Heritage

In the frame of the activities related to the preventive conservation and maintenance of Cultural Heritage, the application of titanium dioxide based treatments on stone surfaces could offer an advanced contribution, limiting the cleaning interventions. The present work has been carried out to verify the effectiveness of these products and the absence of damages on the surfaces. Stone specimens, as calcareous matrixes with low porosity and different colours, were treated with two different TiO2 based products. The first one, commercially available, is a water solution of TiO2 nanoparticles. The second one, under experimentation, consists in a TiO2 functionalized polisiloxane. The homogeneity of distribution on the surfaces was verified by SEM-EDS and the water repellent property of the products was evaluated by measurements of the static contact angle. Since an important requirement for the application of coatings on stone surfaces of artistic and historical interest is the maintenance of the aesthetic characteristics, colorimetric tests were performed on the treated materials. Furthermore, to check the photo-catalytic properties of the TiO2 based products, treated specimens coated with an organic colorant, were submitted to UV irradiation and the relevant changes of colour were measured by a spectrocolorimeter. The obtained results are promising for a future application and a wider experimentation will be planned to investigate the effectiveness of these products and their harmfulness. This will include the most common building stones in Mediterranean area exposed to polluted environment.