How ink is made

Ink is color ground into a liquid fine enough to pass through a printing press without clogging it.

stations: 8
things upstream: 37
raw sources: 15
steps from the ground: 7

The short version

Printing ink starts with pigment wetted by a varnish of resin and oil, using rotating blades to build a thick mill base. Shot mills or three-roll mills then break up the clumps, sometimes over three passes. More varnish and additives thin the base to press strength. Bag filters catch oversize particles, and each batch is tested for tack and fineness.

Ready the varnish

Resin and oil or solvent form the clear vehicle that carries the pigment. A sheetfed offset ink might use a long-oil alkyd or phenolic litho varnish.

Goes in
Vegetable oil Phenolic resin
Wet the pigment

Rotating blades force varnish into clumps of dry pigment, and more oil and resin make a mill base. Carbon black gives black and titanium dioxide gives white.

Goes in
Carbon black Titanium dioxide Pigment
Or flush wet presscake

Flush pigments skip dry clumping. Varnish added to wet pigment presscake displaces the water, which is poured off, and a heavy mixer works the stiff mass. Such inks need much less premixing.
Grind in a shot mill

The base is forced through a chamber where rotating disks drive metal pellets through it, breaking up clumps. Waxes and driers often join here.
Shear on three rolls

Stiff paste inks go between rolls turning at different speeds, and a doctor blade takes the ink off the fastest one. Hard pigments can need up to three passes. Skimping saves money but costs color strength and can wear printing plates.
Thin it to press strength

Base ink is let down with more varnish, wax compound, solvent and additives. One patent turns about 216 parts of base into 833 parts of press-ready ink. Inks for inkjet cartridges are thinned much further with water or alcohol.

Goes in
Water Ethanol
Filter out oversize grit

Bag filters with shrinking pores, starting at 150 microns, trap oversized particles. A magnetic filter may be added for metal fragments.
Test tack and grind

Technicians measure tack, fineness of grind and how fast the ink picks up water. Only then does it go off for packing.

End of the lineInk Next it goes into syringe, plastic bag, credit card and 40 more.

Worth repeating

The earliest Chinese inksticks date to around 256 BC, and they were made from soot and animal glue.
Egyptian red and black inks used iron and ocher as pigments, with lead as a drier.