Secco painting technique revealed in non-restored Pompeian murals by analytical and imaging techniques

Abstract

The fresco technique appears to have been widely used on Roman mural paintings. The close observation of many of such murals suggests, however, the application of a secco technique over the fresco background. In this work, for the first time, fragments from Pompeian mural paintings that had never been restored have been investigated by optical microscopy, reflectance transformation imaging, micro-Energy-Dispersive X-Ray Fluorescence, micro-Fourier Transform Infrared Spectroscopy, and Direct Temperature-resolved Mass Spectrometry. A small number of fragments from restored paintings from the same Archaeological Park was also analyzed by the same techniques for the sake of comparison. The results of this multi-analytical approach that involves - for the first time on this type of samples - scientific photographic investigation, point out to the use of a protein-based medium, most probably egg, to execute the secco layers. On the other hand, wax was ubiquitous in samples taken from restored mural paintings. This last evidence further highlights the importance of selecting appropriate candidates for the study of original organic binders.