Technical non-invasive study of the novo-hispanic painting the Pentecost by Baltasar de Echave Orio by spectroscopic techniques and hyperspectral imaging: In quest for the painter's hand

This paper presents a combination of noninvasive techniques for the study of superimposed painting stages in The Pentecost, a Mexican Colonial panel painting attributed to Baltasar de Echave Orio (1558 - 1619). The application of reflected hyperspectral imaging (HSI) analysis for mapping the distribution of the pigments in the paint surface and the use of ultraviolet (UV) fluorescence photography and X-ray radiography as complementary imaging techniques provide new insights into the making process of the artwork, its manufacturing and conservation state. For a better understanding of the in situ results gathered, we studied a series of paint mock-up samples created following recipes and studio practices from art treatises. The use of spot analytical methods such as fiber optic reflectance spectroscopy (FORS) and X-ray fluorescence spectroscopy (XRF) allowed for a robust identification of the artist's materials.

Identification of natural red and purple dyes on textiles by Fiber-optics Reflectance Spectroscopy

Understanding dye chemistry and dye processes is an important issue for studies of cultural heritage collections and science conservation. Fiber Optics Reflectance Spectroscopy (FORS) is a powerful technique, which allows preliminary dye identification, causing no damage or mechanical stress on the artworks subjected to analysis. Some information related to specific light scattering and absorption can be obtained in the UV-visible and infrared range (300-1400nm) and it is possible to discriminate the kind of support fiber in the near infrared region (1000-2500nm). The main spectral features of natural dye fibers samples, such as reflection maxima, inflection points and reflection minima, can be used in the differentiation of various red natural dyes. In this work, a set of dyed references were manufactured following Mexican recipes with red dyes (cochineal and brazilwood) in order to determine the characteristic FORS spectral features of fresh and aged dyed fibers for their identification in historical pieces. Based on these results, twenty-nine indigenous textiles belonging to the National Commission for the Development of Indigenous People of Mexico were studied. Cochineal and brazilwood were successfully identified by FORS in several pieces, as well as the mixture of cochineal and indigo for purple color.