Canon BJC-2100 Series User Manual page 81

If you are replacing a depleted BJ cartridge, dispose of it immediately.
If you are exchanging BJ cartridges for a special print job, hold the
BJ cartridge with the label facing you and the print head down and
store it in the SB-21 Ink Cartridge Storage Box.
Always hold the BJ cartridge by its sides. Never touch the silver plate,
Note
print head, or the sharp edges around the print head.
Replacing the BJ Cartridge
Using BJ Cartridges 81