HEALTH AND SAFETY CONSIDERATIONS IN PRINTING

262.2.4 Ink Drying and CuringAfter the ink has been applied to the surface to be printed it must bind there toensure it stays. This can happen simply as a result of the ink drying, or can take placein a series of cross-linking and polymerisation reactions that form a film and to bindit to the printed surface. These reactions are known as curing reactions. Ink dryingand curing can happen via. any one (or a combination) of the following processes(Wansbrough, Taylor, & Yuen, 2007):•Oxidation. If drying oil is present in the solvent, it will react with oxygen in theatmosphere and undergo curing reactions. Oxidation is polymerization of the bindersso it is chemical drying type.•Evaporation. Some inks, usually those used in applications where speed isimportant, are designed to dry and cure as the solvent evaporates off. Volatilesolvents such as methylated spirits are usually used, but solvents with boiling pointsabove 120 0 C are used for screen-printing inks to prevent the ink from drying duringapplication.•Penetration. Inks that are printing on porous surfaces are sometimes designed sothat the solvent penetrates into the bulk of the printing surface, leaving dry ink on thesurface. Liquid phase of the printing ink is absorbed in a high rate by the surface ofthe paper and being form paper-printing ink bond one part of the binder is stayed inthe printing inks on surface to keep in together of pigments and this is completed inonly 2 minutes. Evaporation and penetration are physical drying types (Akgün, &Đmer, 2001)•Radiation curing. Radiation (usually UV) is fired at the ink, instigating a series ofpolymerisation reactions. Inks cured with polymerization under UV light. Most ofthe inks that cure with this way are water-based inks. Radiation is chemical dryingmethods.