Previously, for those printers who wish to continue to use standard inks and are unwilling to use UV gloss for certain printing jobs, double-glazing is undoubtedly their most suitable choice. Two coating units are usually located at the end of the press. To eliminate or reduce the possibility of loss of light (glazing oils or substrates), an aqueous coating must be applied between the wet offset ink and the final coating to isolate the offset ink and use infrared light Or heat radiation drying, can be used as the basis for UV coating adhesion. At the same time, every coating machine must have an integrated drying device, which increases the printing machine's external dimensions and equipment costs. However, the range of gloss that such devices can achieve is greater than that of a pure UV printer. In addition to the use of waterborne varnish plus UV varnish, these devices can also be used to apply the same waterborne varnish twice (eg, to increase the final gloss, apply two coats of varnish to the substrate), Or apply two different coatings (eg, applying the standard coating to the first coating unit and applying special effects to the coating through the second coating unit).
There is another model of the double coater: a flexographic printing unit and a drying device are installed before the first offset printing unit to apply opaque white or a special effect primer.