Monte Iato Pots - Experimental Study on Organic Residue Analysis

Abstract: 

“Absence of evidence is not evidence of absence.” This principle is particularly evident in the archaeological record. Various taphonomic processes ensure that only a fraction of the once-living world of ancient inhabitants remains preserved in the soil. Organic materials, by their very nature, are especially susceptible to decay. Over the past decades, the field of residue analysis of ancient ceramics has taken on this challenge, making it possible to render the seemingly invisible visible.

As early as 150 years ago, initial attempts were made to examine ceramics for their contents using chemical analysis.[i] The French chemist Marcellin Berthelot was the first to study lipids in two Gallo-Roman vessels, identifying the fatty acids palmitic acid (C16:0), stearic acid (C18:0), and oleic acid (C18:1 Δ9).[ii] In addition to Berthelot, other researchers such as Sir L. Woolley, J. Hackford, and R. J. Forbes also sought to extract residues from ceramics at Ur during the early decades of the 20th century.[iii] However, it was not until the 1970s that ORA (Organic Residue Analysis) gained significance, thanks to advances in analytical chemistry.[iv] Pioneering in this regard was the work of Thornton et al. (1970), which formed the foundation for the development of ORA over the following 25 years and established the basis of the discipline as we know it today.[v]

Through various chemical analytical methods, it is now possible to identify ancient vessel contents absorbed into the ceramic matrix. These methods reveal specific chemical fingerprints—so-called biomarkers—that allow for the identification of different substances. For example, the chemical signatures of vegetables, beeswax, wine, and marine products can be detected using GC-MS (Gas Chromatography–Mass Spectrometry)[vi] and LC-MS (Liquid Chromatography–Mass Spectrometric Detection)[vii]; oils can be analysed by LC (Liquid Chromatography)[viii]; animal fats by GC-MS and GC-C-IRMS (Gas Chromatography–Combustion–Isotope Ratio Mass Spectrometry)[ix]; and resins by IR (Infrared Spectroscopy), TLC (Thin Layer Chromatography)[x], and GC-MS. Due to the hydrophobic nature of lipids, these are particularly well preserved and can still be detected even after thousands of years.

In the spirit of a “crime scene archaeology” aimed at reconstructing and understanding human actions and behaviours of the past as precisely as possible, organic residue analysis opens up new avenues of research. In line with this approach, ceramics from the indigenous settlement at Monte Iato were analysed for their contents as part of the FWF projects “Between the Aphrodite Temple and the Late Archaic House I–II” and the TWF project “New Wine in Old Bottles—or Old Wine in New Bottles?” (see left), yielding some surprising results.

For example, the analysis of a matt-painted krater (K 10769) produced seemingly contradictory findings. The vessel, locally produced, imitates the Greek shape of a wine-mixing bowl but is decorated in a traditional indigenous style. It is thus a hybrid object that combines different cultural conventions and offers insights into processes of transcultural exchange. The results are all the more intriguing as they indicate the presence of both wine and resin, as well as adipose fats from ruminants. But how are these two contents to be reconciled? Was the same vessel used to mix wine with water according to Greek custom and at the same time to serve meat broth? Could this difference perhaps be explained by the production process and subsequent use? It is conceivable that the vessel’s interior walls were coated with animal fats to seal the surface and make it impermeable to liquids—a practice known from early modern ceramic production. The later use of the vessel as a wine-mixing bowl could then account for these seemingly contradictory results.

Such questions are to be explored through an experimental archaeological approach, which promises new insights into consumption landscapes at Monte Iato on two levels. On the one hand, experimental archaeology allows for the testing and study of ancient craft techniques. In particular, the treatment of ceramic surfaces with organic substances—such as the ethnographically attested polishing of vessels with oil or sealing with resins, fats, or milk—has not yet been systematically investigated in Archaic Mediterranean archaeology. It also remains unclear how such surface treatments, whether applied before or after firing, would appear in chemical analyses. On the other hand, this approach will generate a dataset under controlled conditions that will serve as comparative material for ancient residue analyses.