After a full nodulizing treatment, the ductile iron liquid metal is very reactive with environmental gases or solids. Mold metal reactions will alter the graphite shape to vermicular or flake.   In this study, the metal/mold reactions were enhanced by different sulfur additions into the no-bake mold inserts to study these phenomena and also to artificially produce layered dual-graphite structure in the casting. Thermodynamic and solidification modeling together with sets of different experimental techniques were applied to a test casting with internal core passages representing cylinder head of diesel engine. The effects of surface shape and location in the mold, content and type of sulfur-containing agent, coating, pouring temperature and additional chilling were experimentally studied and discussed. The results could be used to better understand the metal/mold interaction, prevent surface defects or design of dual-graphite structure processes.