Several chemical reactions take place during the heating of a glass forming raw material batch. These reactions are accompanied by a change in batch volume, the release of several (batch) gases and occurrence of melting phases, gas bubbles and foam. Evolution of gas species, such as CO, CO2, O2 and SO3 can be monitored as a function of temperature. From this information, the reaction mechanisms and temperatures can be derived during the fusion of batch into a molten glass. Celsian has developed and used experimental equipment to enable the observation of the melting-in of a batch in transparent vitreous crucibles and simultaneous analysis of the evolved gases from the batch during heating up, melting and fining. The furnace atmosphere during melting and fining is controlled and the effect of different batch compositions on the temperature of fining-onset and fining gas production can be measured. For instance, changes in the furnace atmosphere can strongly influence the fining temperatures and fining efficiency. This paper shows and discusses the application of this equipment to examine the effect of batch preparation techniques (course, fine batch, pellets) on melting-in and fining behaviour.
