Graeco-Roman Egyptian cartonnage from the Egyptian Museum in Cairo, Egypt: Technical and analytical investigation

•Graeco-Roman Egyptian cartonnage from the Egyptian Museum in Cairo.•Visual, optical and analytical investigations.•Layered structure and material characterization.•Orpiment, ochres, Egyptian blue, madder, malachite, atacamite, gypsum, magnetite. Technical and analytical investigations were carried out on a Graeco-Roman Egyptian cartonnage from the Egyptian Museum in Cairo (TR: 20.12.25.6-SR: 5/290). It belonged to Meter son of Kolanthes, as written in Demotic. Complimentary techniques were used in this study; the optical microscope, X-ray fluorescence spectrometry (XRF), Fourier transform infrared spectroscopy (FTIR), and a scan made using an electron microscope coupled with an Energy Dispersive X-ray (SEM-EDX). The layered structure of the cartonnage was unique, as it comprises; a polychrome layer, a calcite-based plaster layer, a mixed mud and sawdust support layer and finishing calcite plaster layer. The predictable textile layer did not exist; instead, small patches of textile were added in some areas of the cartonnage. Besides, the mud and sawdust layer was not a common practice in the cartonnage industry. The pigment colours employed were yellow, blue, red, green, orange, pink, white and black. Yellow was identified as orpiment (As2S3) and yellow ochre (goethite α-FeO.OH + clay minerals), blue as Egyptian blue [Cuprorivaite (CaCuSi4O10)], pink as madder (anthraquinone components), red as red ochre (α-Fe2O3 + clay minerals), orange as an admixture of orpiment and haematite (α-Fe2O3), green as malachite [CuCO3Cu(OH)2] and atacamite [CuCl2.3Cu(OH)2], and white as gypsum (CaSO4·2H2O) and calcite (CaCO3). The black pigment, magnetite (Fe3O4) was detected for the first time in the pigment palette of ancient Egyptian cartonnage. Gilding was applied over an orange bole layer and the binding medium in both the calcite based plaster layers, as well as the polychrome layers, was identified as animal glue.