In an apparatus for vacuum countergravity casting of molten metal, a gas permeable, self-supporting mold is supported in an inverted casting position in an open bottom container with a particulate bed compacted about the mold. The mold may comprise a mold stack having a plurality of mold members stacked side-by side to form a plurality of mold cavities therebetween. The particulate bed may comprise loose, unbonded particulate compacted in-situ about the mold to support the mold stack in the container and press the mold members sealingly together before, during and after filling with molten metal.