Characterisation of pigments and technical features of Byzantine mural paintings from eastern Crete (Lassithi): a diachronic view of reds between the 8th and 16th centuries

• First analysis of pigments of Byzantine mural paintings from eastern Crete (8th – 16th c.). • Multi-analytical methodology for revealing the red pigment composition and utilization over time. • Dominance of red ochres; vermilion (cinnabar) more widespread than previously assumed. • Lime-based binder components identified; secco and mixed execution techniques. • Thermal and humidity-related degradation of red pigments diagnosed and documented. Crete, the largest and most populous Greek island, occupies a central role in Byzantine art. However, eastern Crete (Lassithi) remains underrepresented in art historical and archaeometric literature, limiting a comprehensive understanding of regional Byzantine artistic practices and their development. To address this gap, this paper documents a systematic, multi-analytical study of Byzantine mural paintings from eleven churches in Lassithi (8 th − 16 th century). It focuses on the identification and use of red pigments, and aims to characterize the composition and execution techniques of paintings through a combination of in-situ and laboratory analyses consisting of pXRF, FORS, PLM, SEM-EDS, and μXRD. The results indicate a consistent but variable use of red ochres, vermilion, and red lead. Of these, ochres are the most frequent pigment, appearing in a range of typologies and purity levels. Vermilion, though costly, was more widely used than previously assumed, appearing not only in focal iconographic elements, but also in borders and underlayers. Red lead was also found in mixtures and degraded layers. Data relating to the lime-based matrices suggest the common use of a secco technique, with painters adapting their approach based on material and visual requirements. The results show local continuity in pigment choices and application, with gradual changes over time, contributing new insights into the technical features of Byzantine mural paintings of the region, along with a valuable reference dataset. In addition, several degradation phenomena identified in this study, including the thermally induced pigment transformation and humidity-related chromatic alterations, carry direct implications for conservation practice.