In the days of HP Deskjet 500C/510/550C trio, HP sold official black cartridge refill kits. It was a bit clunky, but you inserted your cartridge to a contraption, pulled some levers in order presented on the device and you'd have an officially refilled cartridge.
The black cartridges on these printers were transparent, held really liquid ink to the brim and the refill device had aluminum, HP branded ink bottles. Oh, the cartridges had air-pillows inside to maintain a positive pressure at all times.
In the days of HP Deskjet 500C/510/550C trio, HP sold official black cartridge refill kits. It was a bit clunky, but you inserted your cartridge to a contraption, pulled some levers in order presented on the device and you'd have an officially refilled cartridge.
The black cartridges on these printers were transparent, held really liquid ink to the brim and the refill device had aluminum, HP branded ink bottles. Oh, the cartridges had air-pillows inside to maintain a positive pressure at all times.