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Every time I print a page with my inkjet printer, knowing that it literally "jets" ink all over the sheet, I'm baffled by how it's immediately dried. I cannot smudge it with my fingers even if I try. They can be instantly stacked on top of each other without anything coming off. Even large photos covering the entire standard A4 page with ink, it's still somehow all dry. It just looks wet for a bit. But it isn't really.

How did they achieve this fancy "insta-drying" ink? How long has this existed? Is this how ink always behaves? I thought it was infamous for making a mess constantly back in the day?

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Part of what is perceived as drying may actually be absorption of the ink by the paper, which of course increases the surface area for drying.

If you print of glossy photo-finish paper that doesn't absorb the ink as well, you will see it takes longer to dry.

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Heated output rollers and precise control of the amount of ink delivered.

Smaller volumes of ink dry quicker so the improvement of the delivery system - nozzle size, targeting helps the drying time.

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The heaters used to explosively boil the ink out the nozzles of a thermal inkjet printhead reach 280 to 300C at the moment of explosion, but only the boundary layer of the ink in contact with the heaters gets that hot, and only for a microsecond or less. The bulk of the ink is only slightly above room temperature when shot out the nozzles.

Pressurized and heated rollers are not used for water-based inkjet printers. That type of ink does not dry by evaporation of the solvent (which is mostly water); it "dries" by absorption into the paper.

Clever design of the solvents and surfactants used in that type of ink ensures rapid wicking into the porous paper. The R&D necessary to achieve this result required 20 to 30 organic chemists working to perfect the inks and media for almost 15 years.

For printing on glossy photo stock or transparency film, special optically transparent coatings on those media are used to absorb the ink- much like the wicking gels used in overnight diapers to absorb and hold urine.

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The ink is also very hot when it is squirted out of the tiny orifices in the cartridge. Some cartridges use resistive heating elements to heat up, expand and squirt out the ink too.

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  • $\begingroup$ This is completely wrong. $\endgroup$ Jun 20 '20 at 5:31

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