In the particular embodiment of a device for removing dissolved gas from ink described in the specification, an elongated ink path leading to an ink jet head is formed between two permeable fluorine-containing membranes. The membranes are backed by air plenums which contain support members to hold the membranes in position. Reduced pressure is applied to the plenums to extract dissolved gas from the ink in the ink path without accumulating scum on the membrane surfaces. Increased pressure can also be applied to the plenums to eject ink from the ink jet head for purging. Within the ink jet head, ink is circulated convectively from the orifice to the deaerating path even when the jet is not jetting ink.