Optical and electron paramagnetic resonance investigations of colour instabilities in amber glass as a function of melting temperature and batch redox conditions

Soda-lime glasses containing different concentrations of iron, sulphate, and coke were melted with various thermal programmes. Optical and low temperature EPR measurements were made. The FeO/Fe/sub 2/O /sub 3/ and S/sup 2-//S/sup 6+/ ratios were correlated with the optical transmittance at 550 nm and the intensities of a set of EPR lines centred at g/sub eff/ sime 6. These new EPR lines are observed in iron-sulphur amber glass when the log sulphide to sulphate ratio exceeds -0.6: this value coincides with better fining conditions.