Example implementations relate to controllers and printers to operate at least one liquid ejection device of a printhead; the liquid ejection device comprising a nozzle and an associated print liquid chamber bearing a transducer to eject print liquid from the nozzle in response to a firing signal; the print chamber being fluidically coupled to a nozzle supply channel; the at least one liquid ejection device comprising a channel coupled to the print liquid chamber and the nozzle supply channel; the channel having a respective actuator to urge print liquid through the print chamber in response to a circulation signal; wherein the controller comprises temperature control circuitry to actuate the respective actuator using a temperature control signal to increase the temperature of print liquid in the print liquid chamber.