Romantic restorations in the Alhambra monument: Spectroscopic characterization of decorative plasterwork in the Royal Baths of Comares

Abstract

The polychrome plasterwork decorations of the Room of the Beds in the Royal Bath of Comares of the Alhambra monumental ensemble have been studied using Raman microspectroscopy and complementary techniques. This area keeps the testimony of the controversial restorations carried out in the 19th century in an attempt to imitate the lost original appearance of the authentic Nasrid plasterwork. Raman spectroscopy and energy dispersive X-ray fluorescence have been employed to identify the pigments and extenders. Scanning electron microscopy-energy dispersive X-ray spectroscopy has been used to gain additional information about the morphology of the painting layers. Additionally, infrared microspectroscopy provided insight into the nature of the organic materials employed as binders. Vermillion, synthetic ultramarine blue, hematite, and carbon black were clearly identified in red, blue, brown, and black decorations by Raman spectroscopy. Green decorations were executed with a copper-arsenic pigment that could not be unambiguously identified although the presence of Raman bands typical of arsenate stretching bands could point to alteration processes of copper arsenite pigments. Regarding the execution technique, the pictorial layer was applied over a preparation layer of white lead that also contained barite using a proteinaceous binder.The presence of anglesite and other phases related to hydrocerussite alteration due to humidity and salts was also evidenced. Finally, a comparison of the materials found in this redecoration with those identified in original Nasrid decorations has been performed, revealing noticeable differences in both the materials and the execution technologies.

Evaluation of Cleaning Processes Using Colorimetric and Spectral Data for the Removal of Layers of Limewash from Medieval Plasterwork

“…The used pigments are natural malachite (K.10300) for probe 1 and cinnabar (K.42000) for probe 2 from Kremer Pigmente GmbH & Co.KG ® (Aichstetten, Germany) manufacturers. These pigments were selected taking into account the results from previous studies, as they are two of the most commonly found in work of this period [ 2 , 13 , 14 , 15 , 16 ]. Two binders were selected.…”

“…Then, we added a layer of whitewash and selected various cleaning processes in order to test them. The base materials were selected taking into account previous work conducted by our team and other researchers in some of the most representative monuments of this period: Cuarto Real de Santo Domingo [ 13 ], the Madraza chapel [ 2 ], the plasterwork of the Alhambra [ 14 , 15 ], and the Real Alcazar of Sevilla [ 16 ]. Regarding the cleaning processes, we selected traditional methods, both physical (such as a scalpel) and chemical, and other techniques more recently used in restoration (polysaccharide-based gels, polyacrylic acids, or cellulose ethers).…”

Raman Spectroscopic Analysis of an Early 20th Century English Painted Organ Case by Temple Moore

“…Raman spectroscopy is now a well established analytical technique for the characterization of pigments and their substrates on frescoes, paintings, and on decorated artefacts comprising a range of materials, including wood, ceramics, and metals [27][28][29][30][31][32][33]. Even in complex mixtures the key spectral band signatures can be identified and correlated with the use of particular pigments either alone or in admixture [34,35] (Table 1).…”

Recent advances in linear and nonlinear Raman spectroscopy. Part XIV

“…They found that using point‐by‐point Raman analysis with portable instruments showed agreement with the results obtained using the laboratory instruments. Arjonilla et al [ 128 ] considered Romantic restorations in the Alhambra monument and used spectroscopic characterization of decorative plasterwork in the Royal Baths of Comares. Klisinska‐Kopacz et al [ 129 ] found Raman spectroscopy to be a powerful technique for the identification of polymers used in cast sculptures from museum collections and found that portable Raman spectroscopy is a suitable technique for the identification plastics.…”