The Unexpected Discovery of Syngenite on Margarito d’Arezzo’s IThe Virgin and Child Enthroned, with Scenes of the Nativity and the Lives of the Saints/I and Its Possible Use as a Yellow Lake Substrate

The oldest painting in the National Gallery collection, The Virgin and Child Enthroned by Margarito d'Arezzo (NG564), dated to about 1263-4, depicts the Virgin and Child in a mandorla, surrounded by scenes of the Nativity and lives of the saints, set within red and decorative black borders, against a gilded background. The materials and technique were investigated using a combination of non-invasive techniques, such as Fibre Optic Reflectance Spectroscopy (FORS) and macro X-ray fluorescence scanning (MA-XRF), and the analysis of a small number of paint samples using energy dispersive X-ray analysis in the scanning electron microscope (SEM-EDS), High-Performance Liquid Chromatography (HPLC), Attenuated Total Reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) and micro X-ray Diffraction (micro-XRD). The results provided evidence for the use of a number of organic colourants, with both indigo and red lake pigments identified. The finding of an unusual compound, syngenite (K[sub.2] Ca(SO[sub.4] )[sub.2] ·H[sub.2] O), is here postulated as a potential substrate for an organic yellow lake pigment. In addition, reference pigments were prepared to explore this hypothesis. Although documentary evidence confirms that yellow lakes were being produced from an early date, there is very little direct evidence for their use in 13th-century panel paintings.