Original article The conservation of the Vecchietta’s wall paintings in the Old Sacristy of Santa Maria della Scala in Siena: The use of nanotechnological cleaning agents Scilla Grassi a , Emiliano Carretti a , Paolo Pecorelli c , Fabrizio Iacopini b , Piero Baglioni a , Luigi Dei a, * a Department of Chemistry and Consortium CSGI e University of Florence, via della Lastruccia, 3, I-50019 Sesto Fiorentino, Florence, Italy b A.T.I., via B. Ciurini, 6 I-50051 Castelfiorentino, Florence, Italy c Estia’ srl, via San Francesco, 9 I-06083 Bastia Umbra, Perugia, Italy Received 7 July 2006; accepted 6 October 2006 Abstract In the present article we report a study on some sodium dodecyl sulphate/propylene carbonate based aqueous micellar solutions developed with the aim of setting up a nanotechnological cleaning system to remove naturally aged polymeric acrylic layers from the surface of the wall paintings in the Old Sacristy of Santa Maria della Scala in Siena (15th century). Being these systems mainly composed of water (more than 70% by weight), the cleaning of the painted surface have been performed with low environmental impact, due to the small amount of the pure organic solvents used (always less than 25% by weight). Furthermore, the aqueous phase constitutes a hydrophilic barrier to the penetration of the hy- drophobic acrylic materials into the porous support. Fourier Transform InfraRed spectroscopy (FTIR), Scanning Electron Microscopy coupled with Energy Dispersive X-rays analysis (SEM/EDX) and in situ capillary water adsorption measurements indicated the efficacy of this cleaning procedure. Finally, the chemical diagnostics investigation enabled to ascertain the presence of both salts (nitrates and gypsum) and the acrylic polymeric material. Ó 2007 Elsevier Masson SAS. All rights reserved. Keywords: Wall paintings; Cleaning; Nanostructured systems; Acrylic polymers; Chemical diagnostics 1. Introduction Siena’s Hospital Santa Maria della Scala, one of the first hospitals in Europe, was created between the 10th and the 11th century along the Via Francigena (we found a quotation in a document of the 1090) [1] with the purpose to care for pil- grims, poor, and for abandoned children. The Hospital was insti- tuted by the canons of the Duomo that managed it until the 15th century when the important complex was placed, after long dis- putes, under the direct control of the Municipality [2]. Over the years the structure enjoyed the benefits of some generous dona- tions and around 1444, the Old Sacristy, also known as ‘‘Cap- pella del Sacro Chiodo’’ was built and decorated by Lorenzo di Pietro called ‘‘il Vecchietta’’ (1446e1449), with a cycle of mural paintings representing scenes of the Old and New Testa- ment, as requested by the Rector Giovanni Buzzichelli. All the paintings were made by means of a secco technique, using or- ganic binders for the application of the pigments. At the beginning of the 17th century, all the paintings in the Old Sacristy were covered by a very thick surface layer of slaked lime (the so-called scialbo) and discovered only in 1930 when a first conservation treatment of the paint cycle was carried out [3]. Then, about forty years ago, all the wall paintings were treated by an acrylic resin that lead to the for- mation of a transparent colourless layer aimed to act as * Corresponding author. Tel.: þ39 055 457 3045; fax: þ39 055 457 3036. E-mail address: dei@csgi.unifi.it (L. Dei). 1296-2074/$ - see front matter Ó 2007 Elsevier Masson SAS. All rights reserved. doi:10.1016/j.culher.2006.10.008 Journal of Cultural Heritage 8 (2007) 119e125 http://france.elsevier.com/direct/CULHER/