How Paper Is Coated Calendered and Finished
Inline blade coating and soft-nip calendering establish surface uniformity, while targeted finishing passes balance visual embellishment against repulpability.
Ultraviolet Spot Varnish
Liquid Coating
Enhancing specific visual areas of a printed package or book cover requires a localized, high-gloss protective finish. An ultraviolet spot varnish is a liquid acrylate coating applied to select regions of a sheet and cured instantly by exposure to ultraviolet radiation. This coating creates a striking contrast between the glossy treated areas and the matte untreated background.
It provides excellent abrasion resistance and helps protect the underlying ink from scuffing during transit. This process is widely used on premium cosmetic boxes and high-end promotional brochures.
Curing Process
The liquid resin contains photoinitiators that absorb ultraviolet light and trigger a rapid polymerization reaction. This instant curing converts the liquid coating into a hard, durable plastic film within fractions of a second. Unlike water-based or solvent-based coatings, this formulation does not require drying time or heat, which prevents the paperboard substrate from losing its natural moisture and warping.
Accurate registration is required to align the varnish perfectly with the printed image below.
Surface Compatibility
Surface energy of the printed ink must be high enough to allow the varnish to wet out completely without reticulation. Low surface energy can cause the varnish to bead up, which ruins the gloss effect.