A continuous ink jet printer comprising an ink gun for forming an ink jet; an arrangement of electrodes for trapping electric charges on ink drops of the ink jet and for creating an electrostatic field for deflecting drops carrying trapped electric charges; and a gutter having an ink-receiving orifice for receiving ink drops of the ink jet which are not used for printing; a gutter flow path for flow of ink from the ink-receiving orifice of the gutter, through and away from the gutter; an air recirculation line for conveying at least some of any air that has passed with the ink along at least a part of the gutter flow path so as to re-enter the gutter flow path either through the ink-receiving orifice or through a connection into the gutter flow path downstream of the ink-receiving orifice; and a vent for venting at least some of the air that has passed with the ink along at least a part of the gutter flow path so as not to re-enter the gutter flow path.