Offset ink is ink that stays firmly on a paper and will not, generally speaking, be removed by water or friction. Pigment inks usually contain other agents than those in standard dye printing inks, and these agents ensure adhesion to the paper. Typically, pigmented inks contain larger particles than other inks; these particles are absorbed by the surfaces they are applied to and are difficult to remove after this point. While water tends to smear simple dye inks, pigment inks, once dry, usually run very little, even when immersed in water. Pigment inks can be used for nearly any purpose that dye inks can be used for, and can even be used as the offset printing ink source for printers.
While the dye in dye-based inks tends to dissolve completely in water, pigment ink usually does not dissolve completely. Because of this, dye-based inks tend to offer a much smoother writing and printing experience. They can also be made to show much brighter, fuller colors. If, however, dye-based inks are exposed to water in even small quantities, the ink will smear over the paper and render the writing or image damaged or unreadable. The larger, undissolved particles of pigment inks, however, are absorbed into the fibers of the paper and tend to be much more difficult to ruin without physically destroying the paper.