This paper deals with the so-called modular kilns, ceramic structures characteristic of the Bronze and Iron Age
periods in various regions of Europe. Despite the interest shown in these material forms in recent years, their
exact function is still unclear. However, the dominant interpretation within archaeological research has tended
to associate them with pottery production. While this hypothesis has been based mainly on macro-observations
derived from settlement surveys and excavations, our aim is to go further by exploring through a material-
analytical approach. A set of samples from the sites of A Fontela and Castromao, in northwestern Iberia, have
been analysed using a set of methods (mineralogical, geochemical, archaeobotanical and organic chemical) to
evaluate the hypotheses on production and use. Although the samples share a similar morphology and tech-
nology, the analytical results reveal differences in the manufacturing processes between the two sites studied.
Local clays, crop by-products and wild plants from the surrounding areas were used in the modelling, but with
different purposes. In some cases, cereal chaff was added as a temper. Organic-chemical analysis revealed traces
of oils of vegetal origin, with high levels of C18:1 fatty acid (probably mostly oleic acid) and its degradation
products, together with phytosterols, such as β-sitosterol, stigmasterol, campesterol, and δ-5-avenasterol. The
organic compounds are compatible with the processing or culinary transformation of acorns, that appeared
persistently in hearths, pots, and storage structures during Late Prehistory in the regio
