Float glass does not have the completely relaxed structure because it has experienced rather rapid cooling during the annealing process after forming in the tin bath. Heating the glass usually leads to thermal compaction, which is one of the disadvantages of float glasses when they are used as substrates for flat panel displays, such as PDP. The structural relaxation also gives changes in the optical absorption of ions in the glass. In this study, the ferrous and ferric ion absorption changes were used for an evaluation of the relaxation in an iron-containing float glass at and below its glass transition temperature. The results were interpreted in terms of local basicity change due to the rearrangement of alkali ions and a brief analysis was presented.
