A method of producing an ink jet printhead includes steps of forming a substrate having defined therein a nozzle chamber for receiving and storing a fluid, the chamber fed at one side by an inlet passage; forming a nozzle plate in-situ on the substrate to define a nozzle opening on an opposite side of the nozzle chamber to the inlet passage; and forming first and second heater elements suspended between the nozzle opening and the inlet passage, the heater elements having two opposite planar sides and positioned to be in direct thermal contact with the fluid stored in the nozzle chamber at both opposed planar sides. The first heater element is formed on a different layer to the second heater element. The first heater element is formed with a surface area larger than that the second heater element.