New evidence of non-traditional Egyptian blue manufacture in the 6th century Ashburnham Pentateuch

The Ashburnham Pentateuch (Paris, Bibliothèque nationale de France, ms. NAL 2334), dated around 600 CE, is an early medieval illuminated manuscript containing five books of the Old Testament. It is one of the most important artworks of its genre, thanks to its pictures that are among the earliest surviving and most extensive biblical illustrations. It is richly decorated with 18 full-page miniatures (remains of the original 69) illustrating scenes from the Genesis and Exodus biblical books. Its production has been assigned on stylistic base to Spain, Northern Africa or Italy. The miniatures of the Pentateuch have been analysed in non-invasive way by means of UV–visible diffuse reflectance spectrophotometry with optical fibres (FORS), spectrofluorimetry and X-ray fluorescence spectrometry (XRF) in order to characterise its palette and to compare it with those of other early medieval manuscripts. The results of this investigation highlighted the wide use of the pigment Egyptian blue, an unusual feature in miniature painting; moreover this synthetic pigment appears to have been produced following a non-traditional manufacture, due to the analytical evidence of a copper/zinc alloy as source of copper instead of the traditional sources used by Egyptians and Romans, i.e. copper, copper minerals or bronze.