Estimation of phase separation rates of PbO–B₂O₃ melts

The rate of liquid-liquid phase separation was experimentally studied in the PbO-B₂O₃ system. The in situ measurements were made by observing the melts with a videocamera continuously as the melts were cooled down from homogenization temperatures at a rate of 2.5 °C/min. The time interval between the beginning and the completion of the darkening of the visual field was determined as a measure of the separation rate. The phase-separation rate was estimated to be at least 900 times larger than that of the metastable phase separation below the liquidus.