Figure 4: Comparisons among values of plant ash glass samples [open symbols: Thessaloniki, various sites (□)] and those already reported in the literature [full symbols: glass from Nimrud and Aphrodisias (■) [2]; glass from Ra’s al-Hadd (●) and Levantine soda ash glass (◆) [12]; Medieval soda ash glass from Italy (▲) [3]]. Number of analysed samples is also shown.