Abstract: Mechanical and electrical characteristics of individual print cartridges are determined and used to generate control information for customizing control of each individual print cartridge. One or more characteristics including nozzle heater resistance, drop mass and drop velocity for individual print cartridges are determined and used to derive offset values for widths of pulses used to drive nozzle heaters in the individual print cartridges. While all three characteristics are preferably used, any one or two may also be used. Once determined, pulsewidths or offsets from nominal pulsewidths to improve or optimize printing using the print cartridges are stored in memory devices located on the print cartridges so that printers utilizing the print cartridges can retrieve the pulsewidth or offset data and utilize it in customizing or individualizing control of the print cartridges.