Department of Physical and Analytical Chemistry, Faculty of Experimental Sciences, Campus Las Lagunillas, Universidad de Jaén, E-23071 Jaén, Spain.
Conservation Department, Council of the Alhambra and Generalife, E-18009 Granada, Spain.
Molecules. 2022 Feb 23;27(5):1490. doi: 10.3390/molecules27051490.
Non-invasive techniques (X-ray fluorescence, XRF, and Raman spectroscopy) were used for the study of the Hispano Muslim wall paintings. Principal component analysis (PCA) was performed on the semi-quantitative XRF results directly provided by the in-built factory calibrations with minimum user manipulation. The results obtained were satisfactory and highlighted differences and similarities among the measurement points. In this way, it was possible to differentiate the decorations carried out on gypsum plasterwork and the wall paintings over lime plaster. The color palette, revealed by combining the results from XRF and Raman spectroscopies, comprised the pigments hematite, lapis lazuli, cinnabar (in poor conservation state), and possibly, carbon. Evidence of past interventions was also provided by PCA on XRF data, which detected the presence of Pb, Ba, and Zn in some areas. Furthermore, the preparation layers have been studied in detail on cross-sections of two microsamples. Several layers of lime plaster with a compact microstructure have been observed. The characteristic of the pictorial layer and the identification of calcium oxalate point to the use of a secco-technique. The main alteration identified was a gypsum surface layer covering the painting and signs of plaster deterioration due to gypsum migration to more internal areas. Finally, the comparison with the observations made by restorers in previous interventions on these paintings revealed the importance of the representativeness gained with the in situ study, which enabled the analysis of a high number of areas.
非侵入性技术（X 射线荧光、XRF 和拉曼光谱）用于研究西班牙穆斯林壁画。对内置工厂校准直接提供的半定量 XRF 结果进行主成分分析（PCA），用户只需进行最少的操作。结果令人满意，突出了测量点之间的差异和相似之处。通过这种方式，可以区分在石膏灰泥上进行的装饰和在石灰灰泥上的壁画。通过将 XRF 和拉曼光谱的结果相结合，揭示出的调色板包括赤铁矿、青金石、朱砂（保存状态不佳）和可能的碳。PCA 还对 XRF 数据进行了分析，结果表明在一些区域存在 Pb、Ba 和 Zn。此外，还对两个微样本的横截面进行了详细的制备层研究。观察到了几层具有紧密微观结构的石灰灰泥。图像层的特征和草酸钙的鉴定表明使用了干壁画技术。确定的主要变质是覆盖在绘画上的石膏表层，以及由于石膏迁移到更内部区域而导致的灰泥劣化的迹象。最后，与修复者在前几次干预中对这些壁画的观察结果进行比较，揭示了原位研究获得的代表性的重要性，这使得能够分析大量区域。
