A dart has a metal bar (1) passing through a ceramic, shaped, dart head (2) and then through a cylindrical ceramic dart stem (3). A sleeve (4) of a carbonaceous or reactive material is provided about the stem (3) or a layer of that material can be fed on the lower face (5) of the dart head (2) (at the interface of the steel and slag). A block or sleeve (6) of suitable reactive material could be positioned on the top face (7) of the dart. The reactive material could be cardboard or paper, or a reactive metal, such as aluminum or magnesium. In each case a chemical reaction with the molten steel will result in an updraft in the steel which clears slag from the area of the tap hole.