an ink nozzle plate has ink discharge channels for discharging ink , and an air nozzle plate has air discharge channels facing the ink discharge channels for discharging air to jet the ink . a power source produces an electric field through the ink at the ink discharge channels , thereby extending the ink meniscus , and the ink is jetted from the air discharge channels by air - flow and the electric field . a heating means increases the temperature of the air nozzle plate , thereby vaporizing water adsorbed in the air discharge channels and stabilizing the ink jet volume .