Abstract: A capillary unit for an ink jet printer, having a nozzle for spraying a jet of ink onto a record carrier. The jet of ink breaks up into a series of droplets at a droplet formation point in front of the nozzle. A charging electrode, with which the ink droplets are selectively charged for subsequent electrical deflection, is arranged in the area of the droplet deflection point. The charging electrode is devised in the form of a plate, arranged perpendicular to the path of the jet, with a through hole for passage of the droplets. The charging electrode is further devised with at least one groove running from the hole to the outer edge of the electrode.