This paper describes the chemical mechanism of the formation of colour centres in soda-lime-silica glass melts, responsible for the absorption of visible light at a wavelength of about 400-425nm, leading to amber colouring. From the results of the study, important information on conditions which increase the amber glass colour intensity can be derived. Experimental melting studies for amber glass forming batches, measurements of the oxidation state during melting plus analysis of the extinction at 400-425 nm of the obtained glass products show the effect of the melting conditions, the composition and oxidation state on the amber colour intensity. Also, the formation of the ions responsible for amber coloration as a function of temperature during cooling of the glass has been investigated.
