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

Technical Non-Invasive Study of an 18th Century Novo-Hispanic Panel Painting

“…In Figure 2, we can observe spectral features related to lipids on 1729 nm, associated with the first overtone of the stretching mode from the methilenic group [2ν a CH 2 ], and combination bands from stretching (ν a asymmetric and ν s symmetric) and bending (δ) modes on 2308 nm, [(ν a + δ)CH 2 ], and 2349 nm [(ν s + δ)CH 2 ]. Such characteristics have been noticed in the works by Pérez et al [7], and Dooley et al [18]. These absorption bands are common all over the paint, and their presence indicates the knowledge of the drying oil to bind the pigments.…”

“…Classification, image analysis, and generation of hypercubes was performed with Harris Geospatial Solutions ENVI 5.5 software. HSI analysis methods used in this work allowed us to generate different images: pseudo color IR; spectral angle mapper (SAM); UV fluorescence; PCA-RGB composite image; and single PC images, which are described in detail in the work of Perez et al [7], and references therein. Such images permit a detailed description of the techniques involved in the manufacture of the Purísima Concepción.…”

“…Mathematically, each PC is determined by a linear combination of the wavelengths, thus providing insights on chemical or physical properties linked with the associated spectra. We have shown in a previous work [7] that it is possible to go even further by considering a multidisciplinary approach for PCA image interpretation, allowing the description of manufacturing details on the studied object.…”

“…Green tones: A single pigment was identified in all the green areas from this painting, found in the representation of emeralds in the imperial crown, and the stems and leaves of the palm and the lily in the lower area. FORS spectra for this pigment have a reflectance maximum between 554 nm and 584 nm, and absorption bands between 696 nm and 717 nm (Figure 9), which together with the IR signature (Figure 10) allowed to identify the pigment as copper resinate [7]. XRF spectra (Figure 11) confirm the presence of Cu in the green areas, but also presents Pb, Hg and Fe, and vermilion or iron earth to change the saturation of the jewel and the volume from the shadows.…”

“…As recent examples of the use of HSI in heritage science studies, we have: the work by Pérez et al [7], where different manufacturing stages were identified in the painting The Pentecost by Baltasar de Echave Orio (1558-1619); the work by Padoan et al [8], in which HSI was used to monitor preservation and aging conditions of historical documents; the study by Sun et al [9], where different degrees of flaking deterioration were evaluated in mural paintings at the Mogao Grottoes by using NIR-his; and the work of Hou et al [10], where a combination of HSI information and multivariable analysis algorithms were employed to create a virtual restoration of ancient Chinese Qing dynasty paintings.…”