Abstract: A non-refillable ink jet cartridge is rendered user refillable in a convenient manner. Hewlett-Packard ink jet cartridge #51626A is modified by sealing the vent hole at the base of the cartridge with a pressure sensitive adhesive tape, and removing the air tight ink fill plug at the top of the cartridge. After refilling with ink, a bellows type inflator bottle is used to inflate bladders within the cartridge making use of an opening in the cartridge. The ink fill opening is re-sealed either immediately before or just after the bladders are inflated, and bile inflator bobble is then removed which releases the air pressure in the bladders causing the bladders to deflate. The deflated bladders cause an area of reduced air pressure to develop over the ink fill level, which prevents the ink from leaking out of the cartridge when the pressure sensitive adhesive tape covering the vent hole at the base of the cartridge is removed.