A smartphone-based innovative approach to discriminate red pigments in roman frescoes mock-ups

The characterization of red pigments in frescoes wall paintings has been great interest for researchers to better understand raw material procurement dynamics, pigment receipts, stylistic evolution and assess their conservation state. In this study a non-destructive colorimetric approach implementing smartphone-based method was developed order be able distinguish between three made from minium, haematite cinnabar minerals, also mixed pigments, preparing mock-ups following the roman receipt described by Vitruvius. Portable FT-IR, Raman spectroscopy, portable XRF visible reflectance spectra analyses were carried out as reference methods smartphone colorimetry results validation. Employing colour sheet control changing lighting conditions, different chemometric approaches have tested, cross-referencing standard analytical with data obtained smartphone. Overall, using only parameters smartphone, Linear Discriminant Analysis Support Vector Classifier tested efficiently classify each sample based on used, low prediction errors. This work shows potential smartphones cheap, fast user-friendly devices screening frescoes, prior selective step before carrying further more expensive specialized analyses.