Abstract: A device for the separation of slag and its retention in a tapping converter which consists of a closure, sometimes referred to as a dart, arranged to be positioned, either manually or automatically, into the tap hole of the converter. The device may include configurations enabling it to seal the tap hole to prevent slag from entering the same or alternately indicate the level of the slag in the converter relative to the tap hole by restricting the tap hole and imparting a swirling motion to the molten metal and slag therein. The device may be formed of material having a specific gravity lower than that of the steel produced in the converter but higher than that of the slag or alternately having a specific gravity higher than that of the steel to facilitate manual placement of the device in the tap hole.