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We study the synthesis and characterization of an innovative TEOS-based composite coating, which could improve previous formulations used in the field of monument conservation. The proposed coating is composed by a tetraethoxyorthosilicate matrix (TEOS), containing an elasticiser [hydroxyl-terminated polydimethylsiloxane (PDMS-OH)] and a non-ionic surfactant (n-octylamine). The specific self-cleaning and antifouling properties are obtained by the addition of different kinds of nanofillers: the commercial TiO 2 nanoparticles, plus two different silica nanocontainers, loaded with the commercial biocide 2-mercaptobenzothiazole. Through a multi-analytical approach, we evaluate the effect of the nanoparticles concentration on the coatings drying rate, on the variation of their visual aspect and textural properties. Our results show that the addition of the silica nanocontainers at 0.05% (w/v) in sol does not change the color of the coating and reduces the formation of cracks after drying. Moreover, the coating charged with nanocontainers undergoes slower drying, thus improving its penetration into the pores of the treated surface. Further tests of photocatalytic and biocidal properties of this new product on different lithotypes and their potential interactions are in progress.

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The colonisation of stone by different organisms often leaves biodeterioration patterns (BPs) on the surfaces even if their presence is no longer detectable. Peculiar weathering patterns on monuments and rocks, such as pitting phenomena, were recognised as a source of information on past colonisers and environmental conditions. The evident inhibition areas for new bio-patinas observed on the marble blocks of the Caestia Pyramid in Rome, recognisable as tracks of previous colonisations, seem a source for developing new natural products suitable for restoration activities. To hypothesise past occurring communities and species, which gave rise to such BPs, we carried out both in situ observations and analyses of the rich historical available iconography (mainly photographs). Moreover, we analysed literature on the lichen species colonising carbonate stones used in Roman sites. Considering morphology, biochemical properties and historical data on 90 lichen species already reported in Latium archaeological sites, we suppose lichen species belonging to the genus Circinaria (Aspicilia s.l.) to be the main aetiological agent of such peculiar BPs. These results seem relevant to highlight the long-lasting allelopathic properties of some lichen substances potentially applicable as a natural product to control colonisation, improving the environmental and economical sustainability of stone restoration.