Inkjet printers

or: tiny ink explosions that refuse to print black

In 1977 a Canon engineer’s soldering iron accidentally heated a syringe full of ink and the ink shot out, which is how a lot of good ideas start¹. Now a print head has hundreds of nozzles, each with a heater that hits around 500 degrees Celsius in a few millionths of a second, flash-boiling the ink so a bubble fires a droplet of four trillionths of a liter, thousands of times a second², and the ink it fires can cost about $2 a milliliter, more than champagne³.

And it still won’t print black because the yellow is empty.

How it works, badly

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A hot soldering iron touched an ink syringe by accident.
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A heater boils a speck of ink, and the bubble shoves out a drop.
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Hundreds of nozzles do this thousands of times a second.
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Then it won’t print black because the yellow is empty.

Wait, is that real?

Yes, your printer is a tiny explosion factory with a markup.

The soldering iron↩

In 1977, at Canon, a soldering iron accidentally heated ink in a syringe, which pointed Canon’s Ichiro Endo toward squirting ink with heat. A team at Hewlett-Packard reached the same idea on its own in 1978. Canon showed a prototype "bubble jet" printer in 1981 and sold a commercial version in 1985.

The tiny explosions↩

In a thermal inkjet, heating elements reach about 500 degrees Celsius for a few millionths of a second and vaporize a sliver of ink; the bubble pushes a droplet out of the nozzle, and when the heater shuts off, the bubble collapses. Cornell researchers studying the process found the ink heats in about 5 microseconds, at almost 1 billion degrees per second. Print heads hold 300 to 600 nozzles, droplets can be as small as four trillionths of a liter (4 picoliters), and the heads fire thousands of drops per second as they sweep across the page.

The ink bill↩

The British consumer group Which? found that official ink for one Epson printer cost $2.04 per milliliter, which it said is more than champagne, decades-old Scotch whisky, or Chanel No. 5 perfume. Official ink can cost up to 286% more than third-party ink.

The fine print↩

The 500 degrees is the heater; the ink itself tops out near 300 degrees Celsius, a limit for boiling water, according to the Cornell work. The $2.04 price is one printer’s cartridge, and plenty of inks are cheaper. Not every inkjet is thermal; Epson’s push ink with piezoelectric crystals instead. Whether yours refuses to print black with an empty yellow depends on the model, and the soldering iron story is company lore whose details vary in the telling.

Sources: MIT Technology Review: tiny bubbles; Cornell Chronicle: from room temperature to 570 degrees; TechRadar: some printer ink really is more expensive than champagne

Last fact-checked October 29, 2026.