A silicon membrane that is permeable to the vapour of a liquid to be distilled, is seeded with a light-absorbing pigment, and used in conjunction with a light-transparent material in one of three configurations as a solar powered still. In the first configuration, the membrane is in the form of a corrugated surface welded to the transparent material along the corrugations, forming a series of channel-like air chambers. This assembly floats on the liquid, the transparent side being on top and exposed to the sun. Vapour condensing in the channels is collected. In the second configuration, the liquid is contained between a sheet of transparent material on top, and a sheet of membrane material underneath. Vapour condenses in a chamber beneath. In the third configuration, membrane material is in the form of a pipe containing the liquid. A second concentral pipe of transparent material surrounds it and ensures collection of the condensate.