A multi-technique investigative approach unveils new compositional insights into the Pompeian red in the Domus di Arianna

This research investigates the iconic red pigments, symbol of the Roman city of Pompeii buried by Vesu- vius in AD 79. Found extensively in wall paintings and in artifacts decoration, the red pigment has left an indelible mark on the history of Roman art and culture. These include iron-based pigments, such as red ochre and sinopia, rare, less stable and toxic pigments like red lead, realgar and the prestigious cinnabar. In addition, recent studies have shown that certain red pigments recognized in Pompeii are the products of thermal transformation of yellow ochre in red ochre due to the intense heat impact of the pyroclastic flow from the eruption. The aim of the research is to recognize the executive techniques and the composition of red pigments in wall paintings in the context of the Domus di Arianna in Pompeii. A multi-technique approach involving portable and non-invasive techniques and micro-sampling-based analyses such as μ-Raman, SEM-EDS and synchrotron radiation high lateral resolution techniques ( μ- XRD), was adopted. The Domus di Arianna is one of the largest houses in Pompeii and well known for the wall paintings polychromy. Built in stages over different periods (from the 3rd century BC to the 1st century AD), it features different architectural styles. The analytical process has been adapted to the pe- culiarities of the domus and optimized, providing CH professionals with an operational protocol for their investigation campaigns aimed at understanding the composition materials and their painting techniques. The analysis of the red pigments composition confirmed the presence of red ochres and mixtures of red ochres with cinnabar and with different lead compounds, including cerussite and laurionite with traces of wulfenite. A comparative analysis of the various wall paintings found in the domus reveals similarities and differences in terms of the ground layers and pigment palettes used during this period. These results are discussed in the context of existing literature which makes no mention of laurionite and wulfenite in the coloration of the wall paintings in Pompeii.