Fig. 4

Different plant ash glass groups from Piscinas Municipales (PMP) compared to published glass reference groups. a Levantine plant ash glass is characterised by low zirconium and titanium contents, while sample PMP 019 has high Zr and Ti consistent with an Egyptian origin; b Th/Zr ratios distinguish plant ash glass produced in the Iberian Peninsula, highlighting once more the similarities between the bulk of the PMP samples with Levantine-type plant ash glass; c K₂O/P₂O₅ versus MgO/CaO ratios clearly separate Mesopotamian and Iberian glasses from Levantine and Egyptian plant ash glass in terms of the plant ash component; d western Mediterranean and Mesopotamian glasses tend to have elevated Li relative to soda contents compared to glass from Egypt and the Levant, underscoring differences in the plant ash component and/or the production procedures. Data sources: Mesopotamian glass from Samarra [23], Egyptian plant ash glass weights [22], Tyre-type (P-1) plant ash glass from various Levantine sites [20, 34] and Iberian glass from Ciudad de Vascos [21]