The manufacturing of the varnish is the first step in the ink manufacturing cycle, involving the incorporation of the raw materials selected to provide the intrinsic characteristics of the ink. In fact, the varnish constitutes the body of the ink: the “structural” properties of the ink depend on the quality and the properties of the resins, diluents and oils (in the case of offset inks) or solvents (in the case of liquid inks) used in the composition of the varnish.
In the case of conventional offset inks, the manufacturing of the varnish consists in dissolving then cooking one or several hard resins in petroleum diluents and/or vegetable oils. This step, frequently automated, is generally carried out in an inerted reactor equipped with stirring and heating systems. The solubilisation and chemical recombinations, vital to obtain the final properties of the varnish, require cycles to be carried out at perfectly controlled rates and temperatures.
In the case of UV inks, the varnish is manufactured by physically mixing the basic constituents of the ink, without any heating. The chemical synthesis of the UV reagents themselves is outsourced.
The varnishes used in liquid inks are formed by cold dissolution of film forming resins in solvents, using appropriate dispersers.