Ink cartridge contains the ink which is used in the printer at the time of printing. The ink cartridge is the replaceable part of the jet printer. Epson printers use thermal inkjet process for the printing. In the thermal jet, the printing process printer resistor heats up with the help of small current and then painting action takes place. If the ink cartridge gets empty or gets fault you can replace it with a new Epson black ink cartridge.