Q: Why do some printers have two balck cartridges. One thin and other a little fatter? If one runs out, the printer won't work without replacing it. Does not make any sense to me.
A: You have a canon. One is a pigment (the wider one) use for text. The other is a dye used for photos and graphics. A dye based ink cartridge mixes better with your dye based colour cartridge offering better tones in your final print. The pigmented black is a truer black which results in crisp and dark text printing.