ORIGINAL PAPER In situ non-invasive characterization of pigments and alteration products on the masonry altar of S. Maria ad Undas (Idro, Italy) Lavinia de Ferri 1 & Francesca Mazzini 1 & Davide Vallotto 1 & Giulio Pojana 1 Received: 27 July 2017 /Accepted: 4 October 2017 # Springer-Verlag GmbH Germany 2017 Abstract A non-invasive characterization study has been per- formed and here presented for the first time on the masonry altar of S. Maria ad Undas, a parish medieval church on the Idro (Brescia, Italy) lakeshore. The determination of painting mate- rials and of alteration products represent the one of the first steps, together with art history studies, of a wider project aimed to the valorization of the site. Images collected under UV light in fluorescence and reflectance mode provided useful informa- tion about the presence of organic residual materials attribut- able to the application of lost gilding details, while the read- ability of some particulars was greatly improved with respect to what observable in visible light. Moreover, near infrared (NIR) images led to hypothesize the presence of green earths in green painted areas. Raman and reflectance spectroscopy allowed the identification of the pigments and of several alteration products, such as plattnerite, which derived by the degradation of the lead-based ones, hydromagnesite, gypsum, and niter, as well as of carbon-based depositions. Keywords Raman spectroscopy . Multispectral imaging . Medieval pigments . Wall paintings Introduction Preliminary and non-invasive investigations represent the first step in the study of artworks. In particular, when dealing with nearly flat objects, imaging techniques offer an ideal ap- proach. In the field of the conservation of Cultural Heritage artifacts they include well-established methodologies such as high-resolution digital photography in visible light, UV reflec- tance and fluorescence, X-ray radiography, IR reflectography, IR false color, trans illumination, trans-irradiation techniques, etc. (Aldrovandi et al. 1988; Cucci et al. 2012) that have been widely applied on paintings and wall paintings since the early 1990s (Delaney et al. 2003; Liang et al. 2004; Carcagnı et al. 2007; Pelagotti et al. 2008; Liang 2012; Legnaioli et al. 2013; Cosentino 2014a, b). The application of Raman spectroscopy (RS) to Cultural Heritage investigation for the determination of constituent ma- terials, pigments, and pigment mixture compositions of art- works is also well documented (Edwards 2004; Edwards et al. 2005; Bersani and Lottici 2016; Mosca et al. 2016). Wall paintings, frescoes, and rock art received particular at- tention due to the additional information obtainable on their conservation conditions, since many modifications in the min- eralogical and chemical composition of materials can be easily highlighted by Raman spectroscopy, permitting also to iden- tify the presence of previous conservation treatments (Edwards 2004). Also, reflectance spectrophotometry, especially in the FORS configuration, is a well-established technique for the characterization of artworks: applications are attested for paintings and frescoes (Bacci et al. 1992; Bacci et al. 1998; Highlights • Three never studied painted masonry altars exist in the Brescia province • A non-invasive characterization of the S. Maria ad Undas altar is presented • UV and NIR imaging allowed formulating hypothesis on pigment composition • Raman and FORS data on pigment and alteration phase compositions are stated Electronic supplementary material The online version of this article (https://doi.org/10.1007/s12520-017-0550-1) contains supplementary material, which is available to authorized users. * Giulio Pojana jp@unive.it 1 Department of Philosophy and Cultural Heritage, Ca’ Foscari University of Venice, Dorsoduro 3484/d, 30123 Venice, Italy Archaeol Anthropol Sci https://doi.org/10.1007/s12520-017-0550-1