The wide range of available inks is one of the factors influencing the advantages of offset technology
Offset printing has advantages over other technologies due to its excellent quality-price ratio and ease of customization. The versatility of the system is closely related to the variety of inks available and the possibilities they offer depending on the characteristics of each job. Let’s get to know them better.
Offset ink is a greasy and consistent material basically made up of three elements:
- Pigment: this is the component that colours the ink. Its chemical structure determines some of its main characteristics, such as brightness, transparency, or colour. It is made of organic and inorganic pigments, and their combination produces inks of different colours.
- Vehicle: this is the liquid where the pigment particles lie, and which is i ncharge of fixing the particles on the printing substrate. It also gives the ink its main properties, such as emulsifying capacity, degree of fixation or level of transparency. There are organic vehicles, such as mineral and vegetable oils, and synthetic ones, such as resins, which are made from chemicals.
- Modifiers: these are additives that, applied in small doses, act on factors such as door, ink discoloration, drying or scratch resistance.
The different kinds of inks in offset printing
Offset technology uses a wide range of different inks, which can be categorized into six main groups: solvent-based inks, water-based inks, greasy inks, UV-LED-cured inks, EB-cured inks, and environmentally friendly inks.
Solvent-based inks have a drying process in which the solvents used in their manufacture evaporate upon contact with the air.
The drying process of water-based inks is very similar to that of solvent-based inks, except that it is carried out by oxidation.
Greasy inks have traditionally been the most commonly used in the industry. They are characterized by their viscosity, the result of dissolving resins in vegetable or mineral oils, and also dries by oxidation. The result is a dry and hard polymer.
Special inks for curing trought ultraviolet (UV) radiation with light-emitting diodes (LEDs) polymerize much faster than traditional inks. In fact, their curing process is near instantaneous and consumes very little energy, which results in cost savings and less environmental impact, since they also produce no waste.
Electron Beam curing inks offer all the benefits of UV curing and also work in cold, which results in even greater savings in power consumption and less waste generation. Moreover, tit is Volatile Organic Compounds (VOCs) free and, so, do not produce any other polluting emissions. These inks have a very high viscosity, which hampers their use in flexography and rotogravure.
In addition to the progress in environmental sustainability resulting from the growing use of UV and EB curing inks, we are also witnessing the development of new ecological inks, which minimize the use of polluting raw materials, and are made from vegetable oils, do not contain solvents and photo initiators, have low migration, and ease the recycling of the substrate to which they are applied.
Factors influencing the characteristics of offset inks
To achieve a given colour, you have to make combinations. The result will depend on elements such as hue, transparency or opacity and gloss.
Both the type of pigment used, and the printing substrate influence the intensity and hue of the colour, while the vehicle can affect the hue and colour value of the ink. The drying times and ink absorption capacity of the ink will also vary depending on the substrate, which also affects the printed colour.
Transparency or opacity is the ink’s ability to hide or show colour. If we need to create a new colour, ideally the inks to be combined should have a low opacity or a high transparency.
Gloss is the ability of the ink to reflect light and depends on the pigment and on its degree of dispersion through the vehicle. The greater the volume of vehicle relative to the pigment, the softer the ink layer and, therefore, the higher the gloss.
At ROTATEK we are experts in the manufacture of rotary and semi-rotary offset presses with modular configuration, customized according to the needs of each printer. Contact us.