Reference Book
allowing the printed product to be handled without spreading before it is fully
dried. This type of drying inks can be used to print on metals.
Evaporation:- Evaporation drying ink dries as the solvent is evaporated into
the surrounding air, leaving a solid film of resin on the paper. It is the passage
of the liquid to a gaseous state. This type of drying ink are used in flexography,
gravure, web offset and other processes where fast drying time is important.
Penetration (absorption):-It is a physical drying process. When ink dries by
penetration most of the vehicle is absorbed into the substrate.
Precipitation:- Precipitation drying inks also called moisture set ink, dry by
reacting with water. Steam or water is sprayed on to the ink after printing
causing the ink to set quickly.
Radiation curing:-Radiation curing causes a wet ink to become solid in about
a second. There are two types of radiation curing - ultraviolet (UV) and electron
beam (EB).
Ultraviolet (UV)-cured inks:- After being applied to the paper UV ink pass
under a strong source of UV light while still on the press. The UV light activates
special molecules in the ink and causes the inks individual molecules to lock
together and solidifies immediately. They are used both in sheet-fed and web
offset presses.
Electron Beam (EB):-EB curing is similar to UV curing except it radiates
electrons directly on to the fresh ink. EB curing inks cure more thoroughly
than UV curing inks do because electron beams are able to penetrate and activate
the entire ink film.Types of Ink
Special formulae are used to produce inks that are compatible with certain
printing processes. The characteristics of ink formulation are determined by
the plates, press units, type of substrates and the basic printing processes. The
common type of inks are Sheet-fed ink, rubber based ink, web offset heatset
ink, web offset coldset ink, news ink, magnetic ink, invisible ink, opaque
ink, waterless offset ink, fluorescent ink, metallic ink, overprint varnishes,
soy ink,etc.
Sheet-fed ink:- Sheet-fed inks dry by oxidative polymerization. They are highly
tacky ink which is required for sharp image defenition. They avoid filling in
of halftone dots and set-off.
Rubber Based ink:- The vehicle in rubber based inks contain cyclized rubber
that allows these inks to remain on the ink train of the press for several hours