Uncovering nineteenth-century Rococo-style interior decorations at the National Military Museum of Cairo: the painting materials and restoration approach

A rare example of nineteenth-century Rococo-style interior decorations was recently uncovered in the National Military Museum of Cairo, Egypt. Samples of the decorations were analysed using different analytical techniques. The sequence of the paint layers was examined with a digital USB optical microscope. Microstructural examination and microanalysis of the samples were conducted using an environmental scanning electron microscope with energy dispersive X-ray microanalysis spectroscopy (ESEM-EDX). The molecular structure of the samples was analysed by Fourier transform infrared spectroscopy (FTIR). X-ray powder diffraction (XRD) was applied to identify the mineralogical composition of plaster samples. The results allowed the characterisation of two underlying layers based mainly on two phases of calcium sulphate. Pigment materials of vermilion, red lead, red ochre, hydrocerussite, carbon black and green earth were identified. Several chromatic hues were produced by different proportions of mixed pigments. Additionally, chromatic alterations in the red layer were reported and discussed. Based on the results of the analyses, a multi-step restoration was carried out. The intervention procedures were cleaning, application of injection grouts, removal of old mortars, reconstruction of missing components of the composition and retouching. Finally, a superficial protection layer was applied to the decorations to prevent any future damage.