Abstract: An ink jet printing system a print head containing nozzles, a replaceable ink container, an ink supply reservoir connecting the ink container to the nozzles of the print head, and a temperature control system for controlling the temperature of the ink in the ink supply reservoir, wherein the parameters T(0); &Dgr;T/&Dgr;t, which permit a determination of the optimal operating temperature for the ink are physically encoded on the ink container to be read by the temperature control system, T(0) being the optimal operating temperature at time 0 and &Dgr;T/&Dgr;t representing the temperature change of the ink over time.