The pollen washes method

Working in close liaison with the biochemical analyses, the pollinic studies analyse the archaeological pollens trapped in organic remains (especially pitch) and in the porous surface of ceramic and lithic vases and tools (pollen washes technique). In both analytical techniques, the pollen identification leads to routine pollinic study, with pollen spectrum characterisation and exhaustive analysis of the relative percentage of the represented taxa. The laboratory created in april 2020 in the University of Bretagne Sud (city of Vannes) is specialised in pollinic studies, especially in pollen washes. The preliminary results obtained demonstrate that the pollen washes technique can provide new insights into the use and consumption of wild and domesticated plants by ancient societies. The pollen washes technique is applied following six successive steps.

After the selection of artefacts, sediment adhering to the artefact surface is collected and placed into a sealed bag; then an initial gentle wash of the whole object surface is carried out to collect a second control sample. These control samples are processed for pollen analysis following standard techniques. The results from the control samples are latter compared with those obtained from artefact washes to evaluate if the pollen signature from the latter is unique and indicative of cultural practices. In order to separate any remaining surficial sediment adhering to an artefact surface from the deeper pollen signal possibly related to a cultural use of the object, and embedded in the surface’s pores and vesicles, multiple and sequential washes of the artefact surface are needed. In addition, separate washes are undertaken on the use surface versus the non-use surface, in the case of millstones or other grinding tools, and from the inner versus the outer surface for food containers or vessels. Theoretically, the pollen signal from the use/inner surface, in direct contact with the processed or stocked plant or plant product, is distinct from the non-use/outer surface, and related to plant use, processing and/or consumption. The ultimate goal is to detect pollen enrichment or anomalies. When anomalies are observed in specific archaeological micro-contexts, these can be qualitatively interpreted as anthropogenic pollen deposition related to cultural plant usage. decompose the organic matter. Using this novel combination of non-pollen palynomorphs and pollen in micro-archaeological contexts (i.e. archaeological artefacts), the potential relationships between the object and the plant processing or the plant-derived product content could be better characterized.
Very recently, a new research route, allowed by the Pollen Washes has been opened, dealing with spores of parasitic fungi of diverse plants and saprophytic fungi that decompose the organic matter. Using this novel combination of non-pollen palynomorphs and pollen in micro-archaeological contexts (i.e. archaeological artefacts), the potential relationships between the object and the plant processing or the plant-derived product content could be better characterized.

Bibliography
Miras Y., Ejarque A,. Barbier-Pain D., Corbineau R., et al. 2018- “Advancing the analysis of past human/plant relationships: methodological improvements of artefact pollen washes”, Archaeometry, DOI: 10.1111/arcm.12375