mx870 ink catridge usage?

[hyepriestess]

the printer sucks up the black ink from the fat 220 cartridge, and leaves the slender 221 black ink cartridges alone.  thus, i have several 221 cartridges sitting here (from color packs) and must continue to purchase the 220s.  any insights?

[jrhoffman75]

220 is used for printing text documents. 221 inks are used for color photo printing. 

You can buy 220 without the 221.