Fig. 6
From: Phosphate: a neglected argument in studies of ancient glass technology
Case Study III. Early medieval and late-Roman Na–Ca flat glass. Left column CH-Sion 7th, and CH-Müstair 9th century. WD-XFA Basel. N = 120. Analyses: Ref. Wolf et al. (2005). a Most analysed glasses contain <0.20 phosphate together with around or over 0.95 Na2O/(Na2O + K2O) indicating possibly the use of geogenic soda. c Phosphate vs main oxides. e Ternary chemical diagram with inserted physical/melting data, probable melting temperature between 850 and 1000 °C. Right column Italian peninsula. Analyses: Data from Arletti et al. (2010) and Verità (1995), N = 80. b Phosphate vs alkali-index. All but 7 analyses display an index >0.95 together with P2O5 <0.20 representing Na–Ca glass, probably made from geogenic soda. d Phosphate vs main oxides. f Ternary chemical diagram with inserted physical/melting data, probable melting temperature between 850 and 1000 °C