Most HP and Epson printers are drop on demand printers. They use electrical pulses to fulfill requests for ink. The ink is expelled out of the print head by a bubble which forms as a reaction to being heated. Once the ink is propelled out of the cartridge, the bubble cools, contracts, and forms a vacuum of sorts, which pulls more ink into the nozzle.

HP DeskJets and BubbleJets are popular examples of printers that use this technology.

Epson printers work on the same principal with the exception of a minor twist ? they use a transducer to produce the droplets in what is referred to as piezoelectric DOD.

So what about the ink ? does it matter what kind you buy as a replacement?

The answer is yes, it does matter.

The ingredients that go into ink play a huge role in the quality of your printouts. All ink manufactures work to strike the delicate balance between print quality, time it takes to dry, and nozzle performance. As you might have guessed, as the print quality improves, the dry time increases.

Manufacturers have to be careful that the ink does not dry too quickly ? there is the danger that it will actually dry on the nozzle. This can ruin your print head, definitely clogging up your nozzle, and reducing the print quality.

Bill Smith is an expert on printers. Read more about printer and ink at http://www.buythebestbuy.com