Applying LIBS, SEM/EDX, and FTIR spectroscopic analysis for the conservation of cairene architectural heritage

This study investigates the wall paintings of Al-Qazdughli Palace, an early twentieth-century landmark in Cairo's historic Garden City district near Simon Bolivar Square, using a multi-analytical spectrochemical approach. As an important example of Cairo's architectural heritage, the palace has experienced extended neglect and significant deterioration. Laser-Induced Breakdown Spectroscopy (LIBS) using an Nd: YAG laser at 1064 nm was used to examine six pigment colors: gold, brown, light green, blue, bright red, and dark red. The gold pigment showed strong signals for Zn, Ag, Ba, Au, Cu, and Pb; Zn was dominant in the brown pigment; and the blue pigment contained Ti, Cu, and Zn. The light green pigment revealed Ca, Cu, Zn, and Pb; the bright red pigment showed Ca, Fe, Cr, Zn, Hg, and Pb; and the dark red pigment contained Ti, Mn, Fe, and Zn. The LIBS findings were confirmed through SEM/EDX analysis, which produced consistent elemental results. Optical microscopy enabled non-invasive examination of paint-layer surface morphology and microstratigraphy. FTIR analysis of selected pigments also identified carbonyl ester bands (1750-1740 cm⁻¹), indicating oil-based binding media. Together, these results highlight LIBS, supported by complementary techniques, as an effective quasi-non-destructive tool for the in situ analysis of wall paintings and for informing conservation and restoration strategies.