A body of sand and binder surrounding a cavity for the reception of molten metal in the production of castings. The cavity must have dimensional accuracy, and the sand surrounding it must be of sufficient stability to allow the metal to solidify in the exact shape of the impression. The production of the sand mold involves making a pattern of the part to be cast, and packing molding sand round the pattern, which when withdrawn leaves the cavity into which the metal is poured, cores being inserted to leave cavities where desired in the casting.