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Ink
How is printing ink used?
Now that we’ve covered paper, the other main ingredient we need for the offset printing process is ink! Most full-color offset printing uses four colors of ink (cyan, magenta, yellow, and black), applied separately via four separate printing plates, to produce millions of colors. This ink makes its way down from the ink reservoir (known as a fountain) onto the printing plate, then onto the rubber blanket, and finally onto the paper itself. The photo below shows four ink fountains on a 4-color press machine.
Ink Fountain
If you look down at an offset press from above, you’ll see four ink fountains — one for each color of ink. Each of these fountains sits at the top of an assembly containing a cylinder that will hold the printing plate and another that will hold the rubber blanket.
Water Solution
Each fountain also has a reservoir of a water-based liquid known as fountain solution. This water solution is rolled onto the printing plate to repel the ink from the areas that will become white space on paper. Digital offset utilizes the chemistry of water and imaging oil solutions to achieve the same effect.
Roller
The roller distributes ink onto the plate in an even, controlled manner, creating consistent ink coverage for the entire plate.