A continuous ink jet printer has a nozzle plate 1 which includes an orifice 3 for emitting a stream of ink. A counterbore 4 surrounds the orifice. A passage 5, 6 is provided which lies substantially in the plane of the plate and intersects the counterbore, and through which a flow of cleaning agent may be supplied to the counterbore, in order to flush ink from the surrounds of the orifice.