Production recipes of mortar-based materials from ancient Pompeii by quantitative image analysis approach: The microstratigraphy of plasters in the Temple of Venus

Disclosing the composition of mortars and plasters adopted in antiquity is of crucial importance from a historical point of view, both to assess the technological knowledge of a given civilization and also from the point of view of conservation of the historical artefacts to proceed with the most appropriate methodologies for conservation. This work intends to increase the analytical capabilities of the specialists to ensure an increasingly accurate and detailed analysis of the characteristics of the mortars used in ancient times. To this aim, the increasingly appreciated and adopted approach in digital image analysis (DIA) has been added to the petrographic study in thin section to obtain a more accurate quantification of the components of the mortar mixtures (binder/aggregate B/A ratio). The approach was carried out on well-known building materials from the Temple of Venus of Pompeii, in particular on stratified plasters whose sequence was found to be particularly recurrent in the materials taken into account during the archaeological investigations. The study revealed a good correspondence between traditional microscopic quantification techniques and digital image analysis, thus guaranteeing the truthfulness of the data obtained through the latter methodology. It also pointed out discrepancies related to the image processing and image types that should be consciously consider when applying this quantitative method. At the same time, however, greater accuracy was found in the data obtained from the DIA.