Now that we’ve covered paper, the other main ingredient we need for offset printing is ink! Most full-color offset printing uses 4 colors of ink (cyan, magenta, yellow, and black), applied separately via 4 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.
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 one that will hold the rubber blanket.
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.
The roller distributes ink onto the printing plate in an even, controlled manner, creating consistent ink coverage for the entire plate.