(57) A method and a device for compensating for loss of metallostatic pressure during the casting of molten metal 1 under gas pressure from a slit 5 in a container 3 onto a moving chilled surface 6 in which some of the molten metal 1 is allowed to penetrate into a chamber 12 maintained at a gas pressure different from the gas pressure in the container 3 and the extent to which the metal 1 penetrates into the chamber 12 is used to control an increasing or a decreasing of the gas pressure in the container 3 to compensate for the loss of metallostatic pressure. Preferably the extent of penetration is sensed by an electrically conductive probe 13 which is part of a circuit closable by the molten metal 1 coming into contact with the probe 13.