Abstract: An apparatus and method for making hollow shell cores wherein a core box assembly is provided including a vented pattern. Baffles are provided in the core box in the space between the pattern and the core box walls whereby a catalyst gas flowing into the core box through an entry port will be caused to enter the pattern and to flow along the outer layer of a sand and binder change in the pattern. The gas will then be caused to flow out of the pattern into a trapped gas vent and out of an outlet port of the core box. The continuous flow of catalyst gas through only the outside layer of the sand and binder charge in the pattern will only cause the outer layer of the charge to be cured and to form a hardened shell. After formation of the shell, the uncured sand and binder mixture in the shell will be discharged and reused. The shell is then transferred from the core box assembly.