The image of Our Lady of Copacabana is a gilded polychrome sculpture manufactured in maguey wood at the end of the 16th century. It is a highly devotional image in the Andean region and her sanctuary lays at the shores of the Titicaca Lake in Bolivia. In this study, a green sample taken from the Virgin´s veil has been analyzed with the aim to identify the green pigment and the gilding technique. The green pigment layer covered completely the shiny color of the gilded area. First, the cross section of the sample was examined by optical microscopy revealing the presence of green crystals on a white layer; beneath it, a gold leaf on a red bole was observed. Scanning electron microscopy-energy dispersive spectroscopy analysis allowed the identification and quantification of copper and chloride in the green pigment layer. Analysis by micro-Raman spectroscopy indicated the presence of atacamite (Cu 3 Cl 2 (OH) 3 ) as the green pigment. Although this compound has been identified as a degradation product of copper pigments or of metallic objects containing copper, in this polychrome sculpture, atacamite was used as the green pigment and is identified for the first time as a mineral pigment in a colonial sculpture made in the Viceroyalty of Peru.

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The Andean church of San Andrés de Pachama is located in the highland of the northernmost of Chile, near the limit with Bolivia and next to the Ruta de la Plata. This commercial route contributed in the past to the transport and commerce of various raw materials, such as silver, from the Andean mountains region to the Pacific Ocean coast and then to the European market. The walls inside the church are decorated with paintings from the end of the eighteenth century that reproduce religious motivs together with flowers, fruits, and birds. In this study, micro samples taken from one of the mural paintings have been analysed to acquire information on the artistic materials and the painting technique previous to the restoration of the paintings. Analysis by micro-Raman spectroscopy complemented with scanning electron microscopy-energy dispersive X-ray spectroscopy, attenuated total reflection infrared spectroscopy, X-ray diffraction, and high-performance liquid chromatography with diode-array detection allowed the identification of orpiment, vermilion, indigo, smalt, antlerite, hematite, carmine lake, and wood charcoal as pigments as well as gypsum as the ground layer. Lipidic and proteinaceous materials extracted from the microsamples were identified by gas chromatography coupled to mass spectrometry and indicated the use of a mixture of egg and siccative oil as binders and a secco painting technique involving animal glue as the plaster primer. Smalt and the prized cochineal lake are reported for the first time in an Andean colonial mural painting.

The image of Our Lady of Copacabana, a gilded polychrome sculpture carved in maguey wood in 1583, is one of the most important devotions in the Americas. In former research, we have identified the use of gypsum, Armenian bole, cerussite and atacamite in its polychromy. In this study, a red sample taken from the Virgin's tunic and a blue sample extracted from the cloak have been analysed with the aim to identify both pigments and offer insights into the painting technique. Analysis by micro-Raman spectroscopy complemented with scanning electron microscopy-energy dispersive spectroscopy and high-performance liquid chromatography allowed the identification of carmine lake in the red sample. Analysis by micro-Raman spectroscopy of the surface of the blue sample and its cross section showed the presence of smalt-the blue-glass pigment-over a cerussite layer, bathed by a very thin ultramarine layer-from a probable native origin-following a pictorial tradition that would last even until the eighteenth century. This is the first time that lapis lazuli has been scientifically identified in a Spanish American colonial painted layer.This article is part of the themed issue 'Raman spectroscopy in art and archaeology'.

This work describes the characterization of green pigments in wall paintings from the Andean churches of San José de Soracachi and Santiago de Callapa in Bolivia, located on an ancient colonial commercial route known as the Silver Route. To approach our goal, microsamples extracted from the mural paintings and mineral samples, from a mine of the same area, were studied by using micro-Raman spectroscopy complemented with micro-energy-dispersive X-ray fluorescence spectroscopy (μ-EDXRF) and scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDS) analysis. The use of gypsum as the preparation layer was detected, and it suggests a secco painting technique. Antlerite, a basic copper sulfate, was identified suggesting a preference for its use as green pigment in the mural paintings of Andean churches that may be related to the local availability of this mineral. Indeed, this study revealed the presence of heterogeneous particles of the basic copper sulfate together with aluminosilicates, quartz and iron oxides among others, which points to a mineral origin of the green pigment because the same compounds were found in the samples taken in the mine. Because a phase transition has been noticed during the Raman analyses, due to a high power of the laser radiation, some tests have been carried out, varying the laser power, and coupling the Raman spectrometer to a temperature-controlled stage to verify under which conditions the degradation of the mineral sample of antlerite occurs