Figure 2: Comparisons among values of natron glass samples [open symbols: Thessaloniki Agora (□); Maroneia (⋄); Thessaloniki, various sites (∆); Thessaloniki glass with moderate 18O enrichment (○)] and those already reported in the literature [full symbols: Roman glass from Europe (■) [2]; Roman glass from Iulia Felix (◆) [3]; 4th century AD glass from Jalame (▲) [2]; HIMT glass from Carthage and Levantine natron glass (bold plus sign) [12]; late Antique-early Medieval glass from Grado ad Vicenza (bold multiplication sign) [3]]. Number of analysed samples is also shown.