is given in K/h for a completely filled crucible and with the electrical output switched off. Smaller furnaces have higher temperature losses than large furnaces. In a 1-t furnace at 1,450 °C, this will produce a figure of approx. 50 K/h and for 12 t approx. 30 K/h. These figures apply for a fully heated crucible and completely closed furnace cover, with the exhaust gas extraction switched off.