Abstract Cathode craters of 50 A arcs have been investigated with surfaces of reproducible definition. It was found, under constant external conditions, that the occurrence of various crater types is a secondary effect due to the surface state, and not a primary property of the arc. At high temperatures (up to 2500 K) the cathode mechanism is not essentially changed, but the crater size increases. This increase can be interpreted by the model of ion-impact heating. The occurrence of large craters at high temperatures explains the enhanced cathode erosion at high surface load as well as the production of large droplets.