A multidisciplinary approach to study the skin of baroque buildings in Salento (Puglia, Italy)

Puglia (Italy) has always occupied a prominent place in the field of production and use of stone materials, because it is rich of limestone with good chemical, physical and mechanical characteristics and with satisfactory colors. As a result these stones have been widely used in recent and past construction in Salento (Puglia-Southern Italy); both carparo and pietra leccese (the names of the most important among these lithotypes) are known since ancient times and have been valued in the art achieving an international appraisal thanks to local handicraft. Over the centuries these stones have produced the complex and well known architecture of Lecce spanning from Romanique to Baroque. The skin of these buildings is an interesting topic because different conservation states can be acknowledged and art historians generally considered a different surface finish the main cause [Casciaro personal communication?]. Unfortunately only the geologist De Giorgi [3] in one of his book, reports that San Nicolò and Cataldo church (a Romanique church) was treated with encaustics, but PyGCMS analyses carried out on a few samples collected before restoration do not agree with this report [tesi? Poster nostro?]. Also workers protected both materials and techniques, making quite difficult today to identify the ancient product and procedures. A recent research reports that between the sixteenth century and the eighteenth century the facades were often left untreated whereas in other periods finishing techniques were applied for aesthetic, hygienic, protective or conservative purposes [1], however no material knowledge is reviewed. The study of literary, historical and oral sources has led to a list of organic products that could have been applied on the building surfaces as waterproof agent: among them, walnut oil, ovine or bovine milk, leaf of the prickly pear, wax, and bulb of the “Drimia maritima” plant [2]. Following this research, a collaborative project started in which all the organic products acknowledged in the different sources have been applied on laboratory samples. These “finished” samples have been aged naturally and artificially and studied by different analytical tools to identify potential biomarkers characteristic of the finishes. For this purpose, a multidisciplinary approach including optical, spectroscopic and chromatographic techniques was carried out and the relevant results will be presented and discussed in the present poster. [1] D. G. De Pascalis, L'arte di fabbricare e i fabbricatori, Nardò, Besa, 2001. [2] G. Siciliano, Tecniche di finitura dell’architettura in pietra a Lecce e provincia, tesi di laurea in “Storia delle tecniche artistiche”, Università degli Studi di Lecce, a.a. 2004-2005. [4] M. R. Derrick, D. Stulik, J. M. Landry, Infrared spectroscopy in conservation science. Scientific tools for conservation, Los Angeles, The Getty Conservation Institute, 1999