The Baroque architecture of Scicli (south-eastern Sicily): characterization of degradation materials and testing of protective products

Scicli and the other Baroque cities of the "Val di Noto" (Catania, Militello, Caltagirone, Palazzolo, Siracusa, Noto, Ragusa e Modica), were recently included in the World Heritage List. These cities were completely destroyed following the earthquake of 1693 and then were involved in an intense period of rebuilding and artistic flowering. In particular, Scicli was reconstructed with the almost exclusive use of a local calcarenite, which belongs to the Ragusa Formation. Due to its nature, this carbonate rock undergoes to many alteration and degradation forms (chromatic alteration, alveolization, differential disaggregation, efflorescence, decohesion, exfoliation and detachment). Therefore, different products (beeswax, vegetable oils, natural and synthetic resins) were used in the past with the aim to preserve the monuments from decay. In this study, through a diagnostic analysis, the degradation materials occurring in the churches of St. Matteo, St. Michele and Carmine in the city of Scicli, as well as residues of treatments carried out in the past, have been identified. In addition, three different types of protective products were tested in laboratory, with the aim of assessing their protective effectiveness in terms of hydrorepellence and response to accelerated aging and salt crystallization tests. Laboratory tests showed that, among the tested products, the Polisiloxane can be regarded as the most suitable for this type of substrate.