This paper addresses the mechanisms of fining (removal of gases from melt) and the effect of batch composition, oxidation state of the melt & furnace atmosphere on bubble removal processes for commercial glass types, such as float glass & container glass compositions. The mechanisms of the different stages of sulfate chemistry in the batch & sulfate fining process are presented, depending on the level of addition of cokes in the batch. The fining gas release as function of temperature from batch & melt are shown for different soda-lime-silica glass forming raw material batches. In case of coke & sulfate containing batches, sulfur dioxide gas release takes place in steps & at different temperature levels. SO2 may evolve from the batch blanket (at about 900 deg C), but also at higher temperatures from the fresh melt starting at about 1050 deg C up to 1250 deg C, some SO2 release can take place up to 1350 deg C & then for oxidised melts a strong evolution between 1420-1500 deg C. The last stage of SO2 evolution from the melt is generally accompanied with oxygen gas formation as well. Bubble growth rates during primary fining & float glass melts from experiments & models are compared & the removal of dissolved gases from such melts is shown. The paper shows that furnace atmosphere may have an important influence on the temperature of fining gas evolution & total fining gas production: water vapour or helium in the atmosphere will reduce fining onset temperature & may significantly increase gas evolution during primary fining.
