A 1/6 th gas-stirred water physical model of a 140 ton steel ladle is used to evaluate mixing in air-water and air-water-oil systems to model argon-steel and argon-steel-slag systems respectively. Thickness of the slag layer is kept constant at 0.004 m. The effect of the gas flow rate (7, 17, and 37 l/min), plug position (0, 1/3, ½, and 2/3 of the ladle radius, R), and number of plugs (1, 2, and 3) on mixing time is also analyzed in this work. Gas is injected at the bottom of the ladle under several plug configurations varying both position and number of plugs. Chemical uniformity of 95% is selected as mixing criterion. Mixing times are experimentally determined when a tracer is suddenly injected into the ladle and the model is instrumented with a pH meter to track the time evolution of the tracer concentration (NaOH 1 M solution) in a given location inside the ladle. Process conditions for best mixing in both water-gas and water-gas-slag systems are: a single plug located at 2/3 of the ladle radius with a gas flow rate of 17 l/min.