How to Preserve an Open Printer Ink Cartridge

Place a piece of paper towel on to a flat surface -- countertop, desk or any other work surface.
Place the open ink cartridge upside-down on the paper towel. You should see the ink cartridge's opening (the small hole where the ink flows out of).
Dampen a soft cloth with cold water from a sink. Wring out excess water. The cloth should be moist, not wet.
Wipe the ink cartridge's opening gently with the damp cloth. Wipe the opening and the area around the opening. If the printer ink cartridge is one with multiple ink tanks, wipe each opening that is uncovered. If you only opened the one color, leave the other tanks sealed with their protective tape.
Cover the ink cartridge's opening with a piece of vinyl tape. If the printer ink cartridge is one with multiple ink tanks, and you removed the protective tape from each one, place a different piece of vinyl tape over each ink tank's openings. Do not use one long piece of vinyl tape to cover the ink tank's openings. Ink from the different tanks can contaminate each other and can ruin the ink cartridge.
Dampen a clean cloth with cold water from a sink. Wring out excess water. The cloth should be moist, not wet. Do not use the cloth you used for cleaning the printer ink cartridge.
Place the damp cloth and the ink cartridge in a plastic storage bag that seals close (Ziploc). The damp cloth will keep the ink cartridge from drying out.
Store the plastic storage bag in a cool, dry place.
Check on the ink cartridge once a week, and re-moisten the cloth with cold water if it is getting dry.