A industrial solid waste from the process of precision casting by lost-wax was used and evaluated for the production of ceramic filters. PU sponges (9.8 ppi) impregnated with a stable suspension were successfully fired at 1550 °C/2 h so that filters well reproduced (9.5 ppi), and mechanically stronger (1.0 MPa) were obtained. The produced filters tested in industrial scale showed very good performances with good filtering efficiency (1.7 kg/s) for liquid cast iron.