Fining Behavior in Alkaline Earth Aluminoborosilicate Melts Doped with As2O5 and SnO2

In this work the gas evolution behavior and the fining ability of the alkali‐free alkaline earth aluminoborosilicate glass batches doped with As₂O₅ or SnO₂ 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 O₂ emission and in evolved O₂ volume between glass batches doped with As₂O₅ and SnO₂. One peak due to reduction of As⁵⁺ to As³⁺ or Sn⁴⁺ to Sn²⁺ was shown in the voltammograms. Glass batch doped with SnO₂ showed better fining in the first fining zone, but batch doped with As₂O₅ is more excellent in the overall fining inclusive of the second fining. This difference in fining behavior was discussed by combination of O₂ 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.