I recently had someone ask: “…how long can an ink jet printer can go unused before head-cleaning uses more ink than regular printing uses…” and the answer to that is easy: head cleaning -always- uses more ink than printing a simple photo. Probably (I’m making an educated guess here) about 10 times as much on average.

The situation with inks drying out is not as simple as your fountain pen skipping.

There are two kinds of inks – pigment and dye. Pigment is little bits of “paint” (Epson encapsulates them in resin) suspended in a liquid (usually water.) Grinding the pigments must be done to high precision so that they suspend, rather than dissolve (as with dye) and are of an appropriate size to pass thru the holes in the print head. Further, they must be significantly smaller (in the case of Epson) because the piezo electric propulsion allows for several different size drops to be dispensed thru those holes.

Pigment inks are often 0.1 microns in size, and the hole in the head is around 20 microns, so it’s not a bunch of particles blocking the hole.

Pigment inks are, as a suspension, subject to settling out, hence the recommendation that the cartridges be shaken. Part of the chemical skill in making an ink and cartridge involves keeping the particles suspended as long as possible. Epson can do it for up to a year or so. (I can’t speak to how well a 3-room Taiwanese third party supplier will succeed at milling, resin encapsulating and suspending, but one suspects that Seiko/Epson are probably more successful at it…)

And this ink dries almost instantly when it contact paper and air. Thus it is invariably dry on the head as well. In fact, it’s the wet ink in the feeder tubes behind the head that must dissolve the dry ink at the mouth. Yes: one of the properties of inkjet ink is that it must dissolve inkjet ink.

What happens then if you let air get in the lines?  There is no way for that ink in the head to be dissolved, because there is no fresh ink touching it, and the air bubble acts like a shock absorber, preventing the ink from feeding.

So, on some professional printers, the heads are parked on a moist sponge when not in use. A cleaning cycle may run ink thru the head under pressure, or may clamp a unit around the head and use suction to try to pull ink out. Commonly, a rubber blade can be run over dirty heads.

Some cheaper printers don’t have separate heads, and the cartridge itself is the delivery mechanism. Some printers use only one size droplet, which is larger, allowing for less refined milling, and hence less clogging.

OK… TMI.

So, what is the cheapest way to keep an inkjet printer running?

Print with it.

Your own environment, the particular printer and the particular inks you use,  will determine how long you can go before your printer needs to run an expensive cleaning cycle. Then print at least one image the day before that time runs out, and you’re good to go.

Or, seen the other way: if I’m right and a cleaning uses enough ink for 10 images, and your time-to-print is once a week, then if you don’t use your printer more than once every 2 1/2 months, I’d start questioning whether or not you were wise to buy the printer in the first place…