A furnace (2) has at least one furnace chamber (20) delimited by a wall (25); at least one opening (5) is provided in the wall (25). The opening is provided with at least one nozzle (50), configured to generate a sealing air flow. A glass semi-finished product (4) can be introduced into the furnace chamber.

The invention relates to a charging apparatus for the dimensionally stable heat treatment of workpieces (1), in particular those of a disk or ring shape, having a charging rack (10) for horizontally mounting the workpiece (1), wherein at least s three screw-type mandrels or ball joint mandrels (2) are arranged on the charging rack (10), the ball joint mandrels (2) having a base plate (3) with a female thread (7), a screw element (4) with a male thread (7) matched to the female thread (7) and a head that has a spherical segment surface, as well as a pressure piece (5) matched precisely to the spherical segment surface of the head and arranged movably thereon.

A furnace (2) has at least one furnace chamber (20) delimited by a wall (25); at least one opening (5) is provided in the wall (25). The opening is provided with at least one nozzle (50), configured to generate a sealing air flow. A glass semi-finished product (4) can be introduced into the furnace chamber.