A multi-analytical approach to the painting technique and the green and blue pigments used in Andean colonial wall paintings

EUGENIA TOMASINI; VALERIA CAREAGA; CARLOS RUA LANDA; FERNANDO GUZMÁN; GABRIELA SIRACUSANO; MARTA MAIER

Bilbao

Conferencia; TECHNART 2017 Non-destructive and Microanalytical Techniques in Art and Cultural Heritage; 2017

Universidad del Pais Vasco

This work shows the results of the application of different analytical techniques to characterize thegreen and blue pigments and investigate the painting technique in Andean colonial wall paintings.Studies were carried out on microsamples extracted of murals from the churches of Soracachi,Curaguara de Carangas, Corque, and Santiago de Callapa in Bolivia. These colonial churches wereCuraguara de Carangas, Corque, and Santiago de Callapain Bolivia. Theseas the Silver Route (S.XVI-XVIII). To approach these goals, an integrated investigation comprisingRaman and FTIR-ATR spectroscopy, optical microscopy, scanning electron microscopy with X-rayspectroscopy (SEMATR spectroscopy, optical microscopy, scanning electron microscopy with XEDS), and mass spectrometry (MS) was carried out. The study revealed a verysimple painting technique consisting on the application of a thin pigment layer on a white groundlayer on the adobe wall. Previous investigations on the wall paintings of the church of Our Lady ofCopacabana de Andamarca in Bolivia indicated a secco technique [1]. The Raman analysis of theground layer in the cross-sections of the samples showed characteristic bands of calcium sulfatecompounds with different levels of hydration: gypsum, basanite and anhydrite [2]. Regarding thegreen pigments, Cu-based minerals, such as brochantite and antlerite, both basic copper sulfates,were identified in most of the green samples. These pigments are uncommon in colonial art and havebeen recently reported in a wall painting of a church in Bolivia [1]. Among the blue pigments, indigowas identified by micro-Raman spectroscopy and direct insertion mass spectrometry [3]. This MStechnique also gave information on the binder mixed with the blue pigment. The characterization ofthe materials used in the manufacture of the wall paintings together with the pictorial techniqueconstitutes a significant contribution to the study of the Andean artistic heritage, which is in manycases the result of the fusion of pre-Columbian knowledge with practices of European painting.