Abstract: A core box has (i) a thermally conductive cope and drag resiliently sealingly mating at essentially a horizontal parting plane, and (ii) core defining walls enclosing an interior and perforated by sand-filtered ports. A sand, resin and liquid catalyst mixture is blown into the interior to form a sand body. At least the outer skin of the sand body is conductively heated to a first temperature (i.e., 300-400.degree. F.); and essentially simultaneously with the conductive heating, the remainder of the sand body is convectively heated by flowing a heated gas therethrough at a second temperature lower than the first temperature (i.e., 250-290.degree. F.). The heated gas enters the sand body from the drag and exits the sand body by way of the cope.