Abstract: A mold core for molding and controlling the temperature of a hollow structure comprises an electrically non-conducting or only slightly conducting inner area and an electrically conducting outer area and two electrical contacts accessible from outside for applying a voltage, wherein the thickness of the outer area is constant or is specifically varied. A method for producing a mold core comprises molding a first body to form an inner electrically non-conducting or only slightly conducting area of the mold core and applying molding material to the first body to form an outer electrically conducting area of the mold core and attaching two electrical contacts accessible from outside for applying a voltage, wherein the thickness of the outer area is constant or specifically varied.