A study is presented which demonstrates the design and optimization of an ink cartridge to be directly connected to the print head and to be used with higher viscous inks. A higher viscous ink is desirable for achieving a smooth drop formation with a low satellite content. On the other hand the increase of ink viscosity will also increase the ink flow resistance within the whole ink supply system. All the commonly used drop on demand firing ink jet heads require a back pressure in the ink supply system for balancing the capillary forces of the nozzle orifices. A high flow resistance of the supply system will add another component to the back pressure of the cartridge, which is dependent of the amount of nozzles fired at a time. This may result in an uneven print appearance - for example areas will print lighter than characters. This is because the ink drop volume is dependent on the negative pressure. Hence the design target for the cartridge should be:• a minimization of the impact of the flow resistance throughout the whole operation window of the print head and cartridge,• an even back pressure curve with a moderate increase during the cartridge ink supply period and• a high ink yield of the cartridge.From a detailed discussion of the design process important parameters are derived, concerning:• the material selection,• the cartridge construction and engineering and• testing and approval.In the result a cartridge functionality is achieved, which allows printing with an arbitrary work load throughout the operation window with small restrictions in the low temperature regime.