A short note on Egyptian blue

Abstract We studied first the feasibility of the reaction synthesis of EB in molten alkaline carbonates; then we changed to “solid phase” syntheses, comparing the yields according to the proportion of the various components. In molten carbonates azurite was produced, which turned to malachite at room temperature. Three “dry ways” were performed: the stoichiometric one, with Na2CO3 as a flux, the Schippa and Torraca recipe, and a “Bolognese” method, which uses NaHCO3 as a flux. Good results in colour and yields were obtained with the Schippa and Torraca recipe, with the stoichiometric molar ratio and with the “Bolognese method” at 860 °C. Research aims. – In the frame of the research carried out on the Roman age wall paintings, the authors put their interest in the checking of the different recipes leading to the synthesis of Egyptian blue. In order to deepen the study of the mechanism of Egyptian blue formation, the synthesis in molten carbonates was tried, but it did not lead to Egyptian blue but to azurite and in the end malachite.