This wetting is necessary to accomplish the metallic bond between the filler metal and the casting. Both the groove faces and the surfaces adjacent to the joint must be cleaned of all contaminants and foreign materials. This includes graphite smears caused by machining. Graphite smears will adversely affect the wetting of the filler metal. Smears can be removed by quickly heating the cast iron to a dull red color with a slightly oxidizing flame and then wire brushing after cooling. Malleable iron, because of its lower carbon content and rough graphite nodules, can be cleaned by abrasive blasting.