EPR spectroscopy provides information about the coordination of transition metal ions, which influence the colour and the radiation heat transfer of glasses and melts. Moreover, EPR signals can be quantified providing information about the concentration of transition metal ions and about their distribution in differently coordinated sites. This study concentrates on ferric iron in some borosilicate and soda lime glasses of industrial interest: neutral glass tubing, flat and container glass. A wide range of situations is reviewed: from clear, low iron samples to high iron green and amber coloured glasses. For each sample the lines observed and the correlation between the line intensity (or the integrated value of the whole spectrum) and the ferric ion concentration, determined using traditional techniques are reviewed.
