A method of and device for heating open melting baths, e.g. galvanizing baths, enameling baths, glass baths and the like, according to which an inert gas is by means of pipes, passages, slots and the like introduced into the respective bath and is withdrawn above the pipes and the like when no articles are to be immersed into the bath for treatment therein, whereas, when articles are to be immersed into the bath for treatment therein, the inert gas is withdrawn outside the path of movement of such articles or outside a device for feeding and withdrawing additional substances into and out of the bath respectively.