Abstract: The double crucible for a glass drawing method has a heatable outer crucible (1) and an inner crucible (2) surrounded by the outer crucible (1), which is heatable separately from the outer crucible (1). Both crucibles (1,2) have an outlet nozzle (1a, 2a) for the glass to be drawn. To make glass fibers from heavy metal oxide glass (HMO-glass) with higher quality and comparatively simple crucible features, the outlet nozzle (1a) of the outer crucible (1) extends a certain distance beyond the outlet nozzle (2a) of the inner crucible (2). Surfaces of the outlet nozzles coming in contact with the glass melt are polished and are provided on a material, which has a reducing action on heavy metal glass in the melt in all cases. These surfaces also have sufficient mechanical strength for and chemical inertness to heavy metal oxide glass.

Abstract: The double crucible for a glass drawing method has a heatable outer crucible (1) and an inner crucible (2) surrounded by the outer crucible (1), which is heatable separately from the outer crucible (1). Both crucibles (1,2) have an outlet nozzle (1a, 2a) for the glass to be drawn. To make glass fibers from heavy metal oxide glass (HMO-glass) with higher quality and comparatively simple crucible features, the outlet nozzle (1a) of the outer crucible (1) extends a certain distance beyond the outlet nozzle (2a) of the inner crucible (2). Surfaces of the outlet nozzles coming in contact with the glass melt are polished and are provided on a material, which has a reducing action on heavy metal glass in the melt in all cases. These surfaces also have sufficient mechanical strength for and chemical inertness to heavy metal oxide glass.