Archaeometrical characterization of the Roman wall paintings from Gades (Cádiz, Spain).

In Roman Baetica and specifically in the city of Gades (Cádiz, Spain), studies about Roman mural paintings has been mainly approached from a traditional perspective, with specific exceptions where archaeometric studies have been carried out on this type of construction and decorative materials. During an archaeological intervention carried out in the Santa Bárbara car park in Cádiz between 2009 and 2012, several Roman mural paintings fragments from the levels of waste deposits were documented. The archaeological record has allowed the levels to be dated between the 1st century BC and the 1st century AD., thus this set of pictorial remains belongs to the Republican phase or to the initial stage of the Augustean period of Gades, a period with hardly any examples of pictorial representations from the early times in Baetica. Due to the number of fragments of Roman paintings with a great variety of colours, several analytical methodologies to know the composition, technique and quality of the paintings were carried out by means X-ray diffraction, X-ray fluorescence spectroscopy, Raman spectroscopy, FTIR, polarized optical microscope, scanning electron microscope, cathodoluminescence microscope and spectrophotometry. A representative set of 31 samples was chosen for this study. Some samples only show a single layer of paint on the mortar, but it is more frequent to find several overlapping layers. The colour palette presents: light and dark blue; bright, light and dark red; purple; light and dark yellow; light green and green; white, brown and lampblack. These colours were identify as egyptian blue, cinnabar, hematite, iron ochers, celadonite, calcite, black, and mixtures between them. On the other hand, the mortars characterization showed two types, the first one is the most numerous and were used as substrate for all identified colours, except for pure black. In fact, fragments that only presented the black pigment, sometimes with lines in white, have been identified on the intonaco layers with ceramic. This remains probably corresponded with a prominent Roman urban villa placed in the Eriteia island of Gades, confirming the importance that this city had within the Roman Empire.

Acknowledgements: This study was financially supported by the Research Project TED2021-132417A-I00 founded by MCIN/AEI /10.13039/501100011033 and by the European Union NextGenerationEU/PRTR, and the Research Project “La gestión de los residuos sólidos en Gades. Aproximación a la caracterización tipológica de los vertidos y su inserción en el entramado urbano de una ciudad costera” (CEIJ-006) Fundación CEiMAR.