Fining Behavior in Alkaline Earth Aluminoborosilicate Melts Doped with As 2 O 5 and SnO 2

In this work the gas evolution behavior and the fining ability of the alkali‐free alkaline earth aluminoborosilicate glass batches doped with As 2 O 5 or SnO 2 were examined, and the redox behavior of As and Sn ion in the corresponding fined melts was investigated by square wave voltammetry. The evolved gas analysis showed a distinct difference at begin temperature of O 2 emission and in evolved O 2 volume between glass batches doped with As 2 O 5 and SnO 2 . One peak due to reduction of As 5+ to As 3+ or Sn 4+ to Sn 2+ was shown in the voltammograms. Glass batch doped with SnO 2 showed better fining in the first fining zone, but batch doped with As 2 O 5 is more excellent in the overall fining inclusive of the second fining. This difference in fining behavior was discussed by combination of O 2 evolution from batches and redox ratio in melts. Finally, it was suggested that the earlier oxidation of As ion in the second fining zone contributed to the excellent fining of melts.