Resumen de UV-accelerated ageing processes on azurite glue tempera paintings: monitoring by spectrocolourimetry, sem-edx, xrd, ft-ir and chemiometry techniques
Natalia Navas, Julia Romero-Pastor, Eloísa Manzano, Antonio García-Beltrán
This work presents a study of UV-accelerated ageing processes on replica samples of azurite glue tempera, pure azurite and pure rabbit glue, all elaborated according to medieval recipes and applied on glass slides. This paper focuses on colour changes and modifications in composition and texture for both pure and mixed samples. Special attention is given to the physico-chemical interactions occurring when azurite and glue are combined. The ageing effects on the replica samples, up to 3000h of UV irradiation, were periodically analysed by scanning electron microscopy (SEM) with X-ray Energy Dispersive Spectrometer (EDS) microanalysis, X-ray diffraction (XRD), reflectance spectrophotometry and Fourier-transform infrared spectroscopy (FT-IR). Once the ageing process ended, a chemometric study using Principal Component Analysis (PCA) of the FT-IR data was carried out independently for each replicate sample and for the composite of azurite replica samples. Results showed the lack of photochemical effect of UV irradiation on pure azurite and when mixed with glue, in agreement with the SEM-EDX, XRD and colourimetry results, contrary to what was obtained for pure glue samples.
