DQFA-Artículos

URI permanente para esta colecciónhttps://hdl.handle.net/10953/276

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Natural or synthetic? Simultaneous Raman/luminescence hyperspectral microimaging for the fast distinction of ultramarine pigments
(Elsevier, 2020) González-Cabrera, María; Arjonilla, Paz; Domínguez-Vidal, Ana; Ayora-Cañada, María José
Genuine ultramarine has been one of the most precious blue pigments employed since ancient times. It used to be obtained by crushing and grinding the lapis lazuli rock and selectively extracting the blue mineral lazurite. Since 1828, when it was produced the synthetic version, the use of this much less expensive material became widespread and synthetic ultramarine blue replaced the natural one in painting palettes. The distinction between natural and synthetic ultramarine is, therefore, an important goal in authentication issues. Here, we present a hyperspectral microRaman imaging analysis, complemented with the characterization of ultramarine pigment samples in terms of colour, elemental composition and identification of crystalline phases by means of fiber optics reflection spectroscopy (FORS), X-Ray Fluorescence (XRF) and X-Ray diffraction (XRD), respectively. We show that a characteristic luminescence signature, easily detected in the course of standard Raman spectroscopic analysis using 785 nm as excitation, is indicative of the natural origin of the ultramarine blue pigments. Furthermore, simultaneous Raman/luminescence hyperspectral microimages allow the distinction between natural pigments of different quality thanks to the different intensity and spatial distribution of the lazurite characteristic band at 548 cm􀀀 1 and those of the luminescent impurities in the region between 1200 and 2000 cm􀀀 1. The establishment of a range of quality between different samples of lapis lazuli was also attempted taking into account the variations in the intensity of the Raman bands located at 548 cm􀀀 1 and 1286 cm􀀀 1. Finally, the feasibility of using the simultaneous Raman/luminescence features for authentication of ultramarine blue in a real historical context, even with non-invasive investigations, is illustrated with examples of different types of blue decorations from several halls of the Alhambra monumental ensemble, in Granada.
Raman and Fourier transform infrared microspectroscopies reveal medieval Hispano–Muslim wood painting techniques and provide new insights into red lead production technology
(Wiley, 2019) Arjonilla, Paz; Domínguez-Vidal, Ana; Correa, Elena; Domene-Ruiz, María José; Ayora-Cañada, María José
This paper describes the study of two Nasrid polychrome wooden ceilings from the Alhambra monumental ensemble using vibrational spectroscopic techniques. The study is focused on the identification of the constituent materials and execution techniques used employing non‐invasive and non‐destructive scientific investigation methods. Information about both inorganic (pigments) and organic (binders and coatings) materials has been obtained without the need for time‐consuming procedures. A complex stratigraphy involving the use of a protective priming layer of red lead covered with animal glue and white lead was revealed. The identification of Raman signatures of different lead oxide compounds, including lead‐tin oxide (Pb2SnO4), in the priming layer, allowed us to hypothesize the synthesis of red lead (Pb3O4) from litharge (α‐PbO), a common by‐product of the cupellation process used since antiquity for silver production. Furthermore, the pigments employed in hidden drawings found in the reverse of the wood pieces of one of the ceilings were also studied and compared with those found in the visible external face.
Romantic restorations in the Alhambra monument: Spectroscopic characterization of decorative plasterwork in the Royal Baths of Comares
(Wiley, 2019) Arjonilla, Paz; Ayora-Cañada, María José; Rubio-Domene, Ramón; Correa, Elena; de-la-Torre-López, María José; Domínguez-Vidal, Ana
The polychrome plasterwork decorations of the Room of the Beds in the RoyalBath of Comares of the Alhambra monumental ensemble have been studiedusing Raman microspectroscopy and complementary techniques. This areakeeps the testimony of the controversial restorations carried out in the 19thcentury in an attempt to imitate the lost original appearance of the authenticNasrid plasterwork. Raman spectroscopy and energy dispersive X‐ray fluores-cence have been employed to identify the pigments and extenders. Scanningelectron microscopy–energy dispersive X‐ray spectroscopy has been used togain additional information about the morphology of the painting layers. Addi-tionally, infrared microspectroscopy provided insight into the nature of theorganic materials employed as binders. Vermillion, synthetic ultramarine blue,hematite, and carbon black were clearly identified in red, blue, brown, andblack decorations by Raman spectroscopy. Green decorations were executedwith a copper‐arsenic pigment that could not be unambiguously identifiedalthough the presence of Raman bands typical of arsenate stretching bandscould point to alteration processes of copper arsenite pigments. Regardingthe execution technique, the pictorial layer was applied over a preparationlayer of white lead that also contained barite using a proteinaceous binder.The presence of anglesite and other phases related to hydrocerussite alterationdue to humidity and salts was also evidenced. Finally, a comparison of thematerials found in this redecoration with those identified in original Nasriddecorations has been performed, revealing noticeable differences in both thematerials and the execution technologies

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Examinando DQFA-Artículos por Autor "Arjonilla, Paz"