Archaeometric investigation on Roman frescoes from the archaeological site of Aquileia

This work reports the results of a multi-analytical study of 21 fragments of Roman mural frescoes found during an archaeological prospection on agricultural fields in the outskirts of a major ancient Roman city, Aquileia (Italy). The research aimed at characterizing the entire stratigraphy (mortars and pictorial layers) of the archaeological samples, in order to increase our knowledge of the production technologies, working techniques and provenance of raw materials in Roman age [1]. The petrographic and textural characterization of the thin section mortars were performed analyzing the distribution and morphology of the mineral grains and pores, the presence of lumps, as well as the binder/aggregate ratio, with the aid of a Polarised Optical Microscopy (POM) and Scanning Electron Microscopy equipped with an Energy Dispersive X-ray detector (SEM-EDX). The results highlight a fine carbonate matrix containing spatic calcite grains in the intonaco mortar, where the aggregate tends to be more angular shaped than in the preparatory layers. Secondary calcite crystals within pores (mainly vughs) were observed, derived by dissolution and recrystallization processes. The presence of lumps reveals also that the lime was produced using the fusion method, the traditional technology for preparing the mortar binder that employs the slaking of the quick lime clods [2]. The fresco painted layers were clearly distinguishable when observed under optical microscope, showing a preponderance of red and yellow pigments, identified as hematite and yellow ochres by μ-Raman and SEM EDX. The common use of these pigments, the composition and morphology of the mortar layers led to hypothesize that the archaeological fragments did not belong to a prestigious building, but rather to common houses [3]. The results of the characterization of these fragments, while contributing to define some aspects of the house estates in the territory of Aquileia, will serve for the development of mock-ups on which to test protective layers aimed at preserving fresco surfaces.