VISCOSITY: is the resistance to flow. If ink flows or pours readily, it has a low viscosity. If it refuses to pour at all, it has a high viscosity.Offset inks usually have a relatively high viscosity.
LENGTH: Ink may be “long” or “short.” Test it by tapping a puddle of ink with a corner of an ink knife and lift the knife up. The ink will follow the knife and stretch into a string. The farther it stretches without breaking,the longer the ink. Offset inks are generally long.
TRANSPARENCY: refers to the opposite of opaque. A transparent ink does not hide the color beneath it, but mixes with it to create a third color. All inks used to print full color work must be transparent.
PERMANENT: Permanent inks maintain their color and do not fade even though exposed to sunlight for long periods. They are especially suited to signs and posters. Permanent inks are also called “fast” inks.
FUGITIVE: A fugitive ink is one that tends to lose its color and fade when exposed to long periods of sunlight.
RESISTANT: Resistant inks are made to withstand the action of gases, chemicals, heat, moisture, or scuffing.