Abstract: A technique for pressurized or differential pressure casting according to the present disclosure provides a riser tube filter formed of ceramic foam having a specific gravity lower than the molten metal to be cast. A riser tube filter according to the present invention may float in and/or on the molten metal within the riser tube and smooth the flow of molten metal within the riser tube simultaneously filtering the metal. As the molten metal is depressurized, a riser tube filter according to the present disclosure will travel back down the riser tube engaging the walls of the riser tube and minimizing the surface of molten metal in contact with the air or other gas. It is emphasized that this abstract is provided to comply with the rules requiring an abstract that will allow a searcher or other reader to quickly ascertain the subject matter of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims.