The effects of carbonisation on the morphology of textile fibres. Comparison between modern and ancient materials: The example of Pompeii

Archaeological textiles are usually rare finds in excavations, as they are generally made of organic material. However, special environmental conditions can cause deceleration or even stop their deterioration yielding unique textile finds. Especially, carbonisation can preserve the textile structure but might also greatly affect the morphology and physico-chemical properties of the fibres, which are the main elements used for their identification. To explore this issue, this paper focuses on the effects of carbonisation on natural fibres, through the case study of the carbonised textiles from the ancient city of Pompeii and their comparison to a set of cellulosic and proteinaceous contemporary textiles that were artificially carbonized in a limited oxygen environment at 250, 350 and 500°C. All carbonised samples were analysed with Optical and Scanning Electron Microscopies (OM, SEM). The research combined the analysis of excavated finds, the available data in literature and experimentation on reference samples. The study showed that the vegetable fibers can better withstand heat, but marked effects on the dimensions of fibres after 250°C. Conversely, the proteinaceous swatches were generally destroyed whereas the archaeological ones do not alter to an unrecognisable degree even at higher temperatures, as long as the material is preserved. This distinct effect seems related to the complete exclusion or extremely limited presence of oxygen in context. This research contributes to a better understanding of the carbonisation process that the fibres underwent during the volcanic eruption of AD 79, offering new data and conclusions concerning their different stage of carbonisation in relation to the events that occurred in their context of deposition. The investigation related to the thermal degradation phenomena on fibres from the Vesuviana area is an important topic concerning not only textile research such as the identification of the raw materials but also the archaeological issue, currently under discussion, about the effect of the volcanic eruption on ancient artefacts caused by the natural disaster and the temperatures reached.