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 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