On the Identification of the a fresco or a secco Preparative Technique of Wall Paintings

The study applies both a minimal and an extended approach for a comprehensive picture of chemical components in wall paintings, including evidence of degradation. Pigments and ligands were characterized via a multi-methodological investigation, including optical microscopy, scanning electron microscopy, Raman micro-spectroscopy, GC-MS, and LC-MS/MS. Particularly, the procedure was tested on wall paintings recently excavated from a Roman domus in Santa Maria Capua Vetere. The hypothesis of a very wealthy owner is supported by the evidence of a multi-layer preparation, a rich variety of pigments, and organic ligands (both terpenic resins and animal glue). The absence of calcite in the pictorial layer (via optical and Raman microscopy) and the presence of organic binders (via GC-MS and LC-MS/MS) clearly indicates the a secco technique.