Characterization of organic materials in the decoration of ornamental structures in the Alhambra monumental ensemble using gas-chromatography/mass spectrometry (GC/MS)

Abstract

The identification of the organic material used in the polychrome decorations of Alhambra complex was carried out in this investigation. Samples from motifs painted on different types of supports, namely marble, wood, and gypsum, were studied. In this way, a comparison on the organic materials used in the marble capitals of the columns from different sites (Hall of the Abencerrages, Hall of the Mexuar, The Court of the Myrtles and the Court of the Main Canal), the Nasrid polychrome wooden ceilings of the Hall of the Abencerrages and the gypsum mocarabes in the plaster decorations of the Hall of the Kings was achieved. This is the first wide scientific study regarding the organic materials employed in the execution of the most representative decorative revetments in the Alhambra monument.Despite the small amount of sample and the complex history of interventions in the monument (both documented and not), results obtained with GC-MS show that proteinaceous materials were mainly used as binders in the different supports and periods studied being animal glue identified in almost all cases. Moreover, wax and lipid materials were also found in the samples from the ceilings, probably as restoration materials applied on the surface of the polychromes on wood. These results shed light on the painting techniques in this extraordinary example of Muslim art in its final European stages, thus contributing to provide scientific information about the still little studied medieval Islamic art.