On earth glass melts with a stable (liquid-liquid) immiscibility show a sedimentation due to the effect of gravity on microphases with different densities. This results in stacked samples which consist of two layers. A microgravity experiment was carried out with a glass of the PbO-B203 system (within the liquid-liquid miscibility gap) to get samples with homogeneously distributed microphases. The glass was melted and cooled under microgravity conditions on board the space station "MIR" using the "CSK-1 Kristallisator" furnace equipment. Electron microscopic investigations show the expected "undisturbed" (not stacked) immiscibility structure if gravity and Marangoni convection (both kinds of microphases have nearly identical surface tension) do not have any influence on phase separation.
