Although the principal factors determining the stability of slag foams have been identified, there is little agreement as to the relative importance of these factors. In this paper the fluid properties, the influence of solid precipitates and the significance of bubble size distributions in the churn flow regime are considered. The slag viscosity appeared to be the most important factor in two-phase systems, while the addition of solids in three-phase systems was observed to stabilise the foam and increase its volume. Investigation of bubble size distributions suggested that liquids with more stable foam have smaller average bubble sizes than liquids with less stable foam. (c) 2005 Elsevier Ltd. All rights reserved.