Scientific analyses of ancient glasses have been carried out for many years using elemental chemical analysis. However, it is known that the control of the redox conditions in the glass melt have a strong implication on the final hue of glass because it affects the Fe2+/[capital Sigma]Fe. Therefore an increasing number of studies of the redox conditions have been published in the recent years by means of synchrotron based X-ray absorption spectroscopy. This is a technique which is not easily accessible and requires dedicated facilities. In this paper we describe an alternative approach by means of optical absorption spectroscopy. We synthesised 10 soda-lime-silica glasses with known redox conditions and iron concentration to calibrate the absorption at 1100 nm in function of Fe2+ concentration. The linear extinction coefficient is also determined. These glasses were also studied by means of X-ray Absorption Near Edge Structure (XANES) spectroscopy. Electron Paramagnetic Resonance spectroscopy is additionally used as ancillary method to verify the quality of our data. Furthermore 28 samples from real archaeological samples were analysed with XANES and optical spectroscopy as a case study. The Fe2+/[capital Sigma]Fe values obtained are compared and demonstrate that the two techniques are in good agreement. Optical spectroscopy can be applied in situ with moderate sample preparation to determine the concentration of Fe2+. To investigate the redox conditions, especially as a first screening approach, this methodology is an important tool to take in consideration before applying more sophisticated techniques such as XANES, which is more elaborate and requires high-tech resources.