Abstract The melt overflow process has been developed as a technique to produce tonnage quantities of strip and fibre in a wide range of materials. Typical thicknesses vary from 150–700 μm depending on liquid alloy surface tension and process parameters. Here a number of crystalline alloys considered for their soft magnetic properties have been cast in air and an enclosed atmosphere. The surface tensions measured by a modified oscillating droplet technique indicate that small impurity concentrations can markedly affect strip properties. As yet no strong reduction annealing effect on coercivity has been established.