  Ice templating, a route where ice crystals are used to template
macroporosity, has been used to process a variety of materials with one level
of macropores. We demonstrate here a variant of ice templating based on the
solidification of mutually miscible solvents. The solidification of different
phases, each defined by their own size and morphology, provides a simple
one-step processing route for materials with hierarchical porosity defined by
up to three levels of macroporosity. These concepts are demonstrated with both
ceramic (yttria-stabilized zirconia) and polymer (polyvinyl alcohol) materials.
