There is disclosed an ink jet printhead which comprises a plurality of nozzles (3) and one or more heater elements (10) corresponding to each nozzle (3). Each heater element is configured to heat a bubble forming liquid in the printhead to a temperature above its boiling point to form a gas bubble (12) therein. The generation of the bubble causes the ejection of a drop of an ejectable liquid (such as ink) though the respective corresponding nozzle, to effect printing. Each heater element is substantially covered by a conformal protective coating (77) which has been applied to all sides of the heater element (10) simultaneously so that the coating is seamless.