method and apparatus for cooling a heated mold of a device for blow - molding thermoplastic containers , the device including : a mold having an internal face which delimits a molding cavity and which includes an external face which surrounds the molding cavity ; heating elements for heating the mold to a determined temperature and which are deactivated when the cooling method is implemented ; characterized in that the mold is cooled by circulating heat - transfer fluid directly in contact with the external face thereof .