PURPOSE: To provide a titled resin which can improve remarkably the strength of a casting mold and consists essentially of a resol type phenolic resin by compounding a novolak type phenolic resin and lubricant with a phenolic resin which is brought into reaction by using LiOH and ammonia as a catalyst.

CONSTITUTION: The phenol is brought into reaction by using 1.0W2.5mol formaldehyde by 1mol phenol and using 0.002W0.2mol LiOH and 0.05W0.8mol ammonia by 1mol phenol in combination as a catalyst. The novolak type phenolic resin and lubricant are compounded with such resulted product of reaction. The high shell strength is obtd. if such compsn., is used for production of resin-coated sand by a shell mold method.