The absorbing spectra of iron-containing glasses and an amber glass were recorded in the temperature range of 25-700 deg C. A shift of the UV absorption edge towards lower wave numbers with increasing temperature was found. The amount of the shift depends on the Fe3+ concentration. Here, the UV absorption edge may superimpose or even cover up the absorption bands of colouring ions with increasing temperatures. For an amber glass sample, with increasing temperature, the intensity of the absorption bands of the amber chromophore decreases slightly. However, above 550 deg C the decomposition of the chromophore is observed. All changes are reversible when temperature is decreased again. The decomposition of the chromophore and the attributed temperature range are in agreement with thermodynamic calculations.
