Offset printing uses inks that, compared to other printing methods, are highly viscous. Typical inks have a dynamic viscosity of 40-100 Pas.
There are many types of paste inks available for employment in offset lithographic printing and each have their own advantages and disadvantages. These include heat-set, cold-set, and energy-curable (or EC), such as ultraviolet- (or UV-) curable, and electron beam- (or EB-) curable. Heat-set inks are the most common variety and are "set" by applying heat and then rapid cooling to catalyze the curing process. They are used in magazines, catalogs, and inserts. Cold-set inks are set simply by absorption into non-coated stocks and are generally used for newspapers and books but are also found in insert printing and are the most cost-conscious option. Energy-curable inks are the highest-quality offset litho inks and are set by application of light energy. They require specialized equipment such as inter-station curing lamps, and are usually the most expensive type of offset litho ink.
Inks
Letterset
Letterset inks are mainly used with offset presses that do not have dampening systems and uses imaging plates that have a raised image.
Waterless
Waterless inks are heat-resistant and are used to keep silicone-based plates from showing toning in non-image areas. These inks are typically used on waterless Direct Imaging presses.
Single fluid
Single Fluid Inks are newer ink that uses a process allowing lithographic plates on a lithographic press without using a dampening system during the process.
Ink/water balance
Ink and water balance is an extremely important part of offset printing. If ink and water are not properly balanced, you can end up with many different problems such as scumming, trapping, and ink density issues can occur. With the proper balance, the job will have the proper ink density and should need little adjustment as soon as balance is met.
|
|
