The aim of the project is to use radio-wave interferometry to determine the BOF slag and metal heights in both a quiescent and a blowing BOS convertor. The hydrodynamics of the slag/metal emulsion and 1, 2 and possibly 3D representations of slag and metal movements during the blowing phase will be made. Process factors such as vessel shape, lance movements, bath agitation, flux/ore additions and fume generation will be considered.