What is print finishing - coating systems

Various coating systems are used in print finishing. These systems differ in terms of the type of coating and the corresponding drying process.

Oil-based varnish. Oil-based varnish is a colourless, oil-based varnish with a chemical composition similar to that of standard offset printing ink. Applying an additional colourless layer of varnish over the printed colours creates a smooth, transparent and resin-rich surface that reflects light more effectively, thereby creating a glossy finish. It dries through oxidation. Its use is now rather rare.

Dispersion varnish. Dispersion varnish is a water-based varnish containing acrylic resins in its chemical composition. An additional varnishing unit on the printing press is required for application. The varnish is applied over the entire surface and dries very quickly using hot air or IR drying. Dispersion varnish offers a very high level of mechanical protection and is therefore often used for rapid further processing. The gloss effect plays a rather secondary role.

UV varnish. In offset printing, UV varnish is a key print finishing technique that offers both visual and functional benefits, ranging from brilliant colour effects to robust surface protection. Its chemical composition is complex and essentially consists of three components. The photoinitiators trigger the chemical reaction upon exposure to UV light. Reactive acrylate binders are used to form the film. Monomers and oligomers are cross-linked by UV light to form a solid film. The use of UV varnish requires an additional coating unit in the printing press and UV lamps for drying. Offline coating on a coating machine is also possible. Coating can be applied over the entire surface or selectively, with a very high gloss effect, particularly in print finishing.