The structure of immiscible alloys depends on the temperature gradient and the gravity force during solidification. The temperature gradient causes Marangoni movement of the droplets and the gravity force causes sedimentation or flotation of the droplets. In gradient experiments performed under normal and reduced gravity it is possible to distinguish between these two effects. This paper presents and analyses theoretically the results of experiments on Zn-Bi and Cu-Pb alloys, performed on earth and in the reduced gravity of space.