“…However, it is also apparent that natron was transported to various sites in the Empire, where local sand was used to produce primary glass. This is described in the writings of Pliny the Elder in the 1st century AD (Silvestri at al., 2006), and can be concluded from finds in western Germany (Wedepohl and Baumann, 2000), in Britain (Baxter et al, 2005) and partly from colourless glass of Iulia Felix shipwreck (Silvestri et al, 2008 and references therein). Isotope ratio analyses of Sr and Nd were made by several authors to indicate the source of the sand (Wedepohl and Baumann, 2000;Degryse and Schneider, 2008;Freestone et al, 2003;Brems et al, 2012Brems et al, , 2013Ganio et al, 2012).…”