| Each form of printing requires a separate type of ink. Since motorists
don't pump diesel fuel into a typical gasoline-powered engine, so, too, is it impossible
to use the same type of ink on every printing press. Here's a sampling of the various inks used today: News Ink
Newspapers with large web presses that print on lengthy rolls of paper
use news ink. Since newsprint is absorbent, the oil in the ink is taken into the paper,
leaving the pigment on the surface. News inks are high in oil content, with black ink
containing as much as 75 percent soybean oil (the remainder is usually carbon black).
Color news ink contains up to 50 percent soybean oil.
Commercial printers use smaller presses that print one sheet of paper at
a time on both coated and uncoated papers. With coated paper, the ink must dry much
quicker than on web presses. Ink for this application contains more resins and 20 to 30
percent soybean oil.
Magazines are published on large web presses using big rolls of paper.
However, this paper often is coated stock and absorbs less oil from the ink. As a result,
a heat-set press passes the printed paper through a high-temperature oven to
"set" the ink on the paper. The oven evaporates volatile organic compounds in
the ink, allowing it to dry quickly. Heat-set inks contain 25 to 35 percent solvent, and
less than 20 percent soybean oil.
Magazines, newspaper inserts, catalogs and directories usually are
printed with cold-set ink on web offset presses on absorbent paper. Cold-set inks contain
about 30 percent soybean oil. They have a paste-like consistency and are designed for
open-fountain equipment.
Presses that print business forms use lengthy rolls of paper that are
almost exclusively uncoated stock. Business forms ink typically has 40 to 50 percent
soybean oil.
These inks are water- or solvent-based, and do not contain oil. However, many applications contain soy protein, which binds the pigment to the surface of the paper. Ink manufacturers indicate the dry material on the paper has about 15 to 25 percent soy protein in the vehicle. Flexographic printing primarily is used for packaging. |
