Patent ID: 7448729

Claim:
An inkjet printhead comprising: a plurality of nozzles; a bubble forming chamber corresponding to each of the nozzles respectively, the bubble forming chambers adapted to contain ejectable liquid; a heater element disposed in each of the bubble forming chambers respectively, the heater element configured for direct contact with the ejectable liquid, such that heating the heater element to a temperature above the boiling point of the ejectable liquid forms a gas bubble that causes the ejection of a drop of the ejectable liquid from the nozzle; and, a print engine controller to control the ejection of drops from each of the nozzles such that it actuates any one of the heaters to eject a keep-wet drop if the interval between successive actuations of that heater reaches a predetermined maximum; wherein during use, the density of dots on the media substrate from the keep-wet drops, is less than 1:250 and not clustered so as to produce any artifacts visible to the eye.