A spherulizing furnace for manufacturing vitreous beads, including a chamber; means for heating the chamber; feed means for delivering a particulate feedstock to one end of the chamber; and means for collecting vitreous beads from another end of the chamber, wherein the chamber includes a pair of opposed walls which are spaced apart by a distance less than their breadth and which are angled to the horizontal so that the chamber has an upper end and a lower end, the feed means is arranged to deliver feedstock to the upper end of the chamber so that the feedstock can pass through the chamber under gravity, and the means for heating the chamber is arranged to heat at least one wall of the pair of opposed walls so that feedstock passing between the pair of opposed walls is heated by radiant heat.