Multi-analytical investigations of earthen wall paintings from the Templo Pintado: stratigraphy and material characterisation for conservation assessment

Earthen wall paintings present complex multilayer structures susceptible to long-term physicochemical deterioration. This study presents a multi-analytical characterisation (optical microscopy, XRD, Raman spectroscopy, SEM-EDS) of previously uncharacterized fragments from Sector 3 of the Templo Pintado (Pachacamac, Peru), extending the analytical coverage of the site and assessing the continuity of material and technological features across the monument, while re-examining the long-standing hypothesis of organic binders. The results reveal jarosite-based yellow pigments, haematite-rich reds, and silicate-carbonate plasters containing illitic and chloritic phases, with evidence of multiple repainting phases. Weak but consistent Raman signals in the 1200–1700 cm−1 range indicate the presence of organic compounds, possibly of plant-based or resinous origin, although their definitive assignation as original binding materials is limited by the analytical methodology employed. The detection of anatase suggests later conservation interventions. Overall, the dataset provides a reference framework for distinguishing original materials from subsequent additions and supports conservation assessment.