The origin of the blue colour of protohistoric vitreous materials from Paduli (Colli sul Velino, Rieti, Italy)

The present study aims at ascertain the valence state speciation of the transition elements (Cu and Co) suspected to play a role in the origin of the blue colour of protohistoic vitreous materials. The case study is provided by 5 different glass artefacts coming from Paduli (Colli sul Velino, Rieti, Italy), where a relevant ability in controlling chromatic effects has been reached by opportunely mixing the two elements, and controlling the thermal process. Only an accurate X-ray Absorption Spectroscopy (XAS) investigation could allow to ascertain the effective metal speciations in the artefacts, thus providing a clue in the understanding of the technological process active in the area.