The article presents results of physical modelling of phenomena occurring during the process of blowing steel by inert gases. The aim of the research was to determine the optimal ceramic material for the porous plugs. Three different materials varying in porosity were tested. Water model of industrial tundish with nominal capacity 320 Mg was used in research. This model was made at 1:10 geometrical scale. Results of the research were presented graphically in the form of Resistance Time Distribution (RTD) curves and graphs of mixing efficiency for particular ceramic materials