As a measure against abnormal jetting caused by the nozzle of the print head drying after evaporation of the ink, the authors attempted to refresh the ink by installing an ink circulation path in addition to the conventional nozzle shaking which mixes the ink in the nozzle by means of piezo vibrations. On understanding the advantages of nozzle shaking and the ink circulation path on this structure, the use of both measures provided the authors with a complementary and highly reliable method for preventing any increase in viscosity. Using a hyper-speed camera they also observed an unusual behavior where the nozzles in non-jetting conditions begin to jet again as the non-jetting time increases. This phenomenon affects printing stabilization and can be well explained by the assumption that inkjetting occurs because of advection and lowered viscosity of the ink.