121 at the end of the drawing furnace and conveys a signal on to the regulator 133 which after consideration of the temperature gives the setting or adjusting command for the energy supply through burner 112 for the preferably independent regulation of the nozzle and the nozzle orifice heating an energy supply is provided having with large installations apparatus for the use of exhaust heat for example recuperators and preheating of the mixture the object of the energy feed regulation is a constant temperature corresponding to the theoretical value in the portion of the smelting furnace which is located directly in front of the nozzle or in front of the drawing chamber respectively the theoretical value of the temperature at the end of the smelting furnace is adjusted normally in this connection from the point of view of glass technology and only in exceptional cases according to other criteria the exception occurs for example if the production mixture in spite of emptying of the full hydrostatic height in front of the nozzle is too small and the glass temperature for raising of the outflow speed of the glass from the nozzle must be raised the control technology combination of the individual control steps is shown by the main portion of fig6 suggestions for the theoretical value of the nozzle orifice 115 which are determined from the actually measured values 126 1 126 n of.