Early Medieval Egyptian blue in laser light

Photo and Raman microscopy image of a patch of the pictorial layer of the mural fragment from the church St. Peter above Gratsch in South Tyrol , Figure: Dariz/Schmid - Research team elucidates complex spectrum of trace compounds in the first artificial pigment of mankind Art technologist Dr. Petra Dariz and analytical chemist Dr. Thomas Schmid (School of Analytical Sciences Adlershof SALSA at Humboldt-Universität zu Berlin and Bundesanstalt für Materialforschung und -prüfung BAM) identified Egyptian blue on a monochrome blue mural fragment, which was excavated in the church of St. Peter above Gratsch (South Tyrol, Northern Italy) in the 1970s. The fragment was preserved in the archive of finds of the office for archaeology of the autonomous province of South Tyrol and served as a reference material for age determination within the frame of a research project on Early Medieval stucco fragments of this church, co-funded by the South Tyrolean provincial museums. The two researchers originally stemming from South Tyrol conducted the project in the laboratories of SALSA and BAM in Berlin. The results were published in the Nature Research journal Scientific Reports. Egyptian blue can be synthesised by heating a raw material mixture consisting of quartz sand, limestone, copper ore and a flux (soda or plant ash) to about 950°C. Around the turn of the eras, Roman sources report that a certain Vestorius transferred the originally Egyptian technology to Pozzuoli.