Now more than ever, there are many coating options available to you that can be done in-line on offset presses. With these options, come innovative production processes that offer you greater creative freedom. An understanding of the basics will give you the information you need to make the best choice for your design and budget.
Varnish is a clear ink film that provides sheen and protection to your press sheet. Varnishes can be inexpensively used as spot varnishes or flood varnishes. Spot being a varnish applied to a specific area of the sheet while a flood varnish is applied across the entire sheet. To employ varnish they set up a unit on the press just like inks, therefore requiring a plate. Gloss, dull and satin varnishes are available and can be used on their own or in combination to create contrast effects. Varnish is also a protectant used to minimize fingerprinting, marking and chalking. On dull, matte, uncoated and C1S stocks, it seals the inks to improve abrasion resistance. When utilized on uncoated stock, it is absorbed into the sheet and is not visible. If you want to create greater contrast or enhance the properties of varnish on dull or gloss stock, the dry trapping would be a technique to consider. Dry trapping simply means that after printing the colored inks, the sheets are allowed to dry before going back through the press to print the varnishes. This second print pass provides better holdout and less absorption of varnish into the ink.
Aqueous coating is similar to varnish but is a water-based substance. Applied through a coating tower on the press, aqueous coating does not require plates for an overall application. Aqueous looks and acts very much like varnish, with all the same sheens available, but can be more cost effective when applied overall. Aqueous blankets can be purchased for spot applications.
Another option to consider is UV coating. Presses must be configured with UV lamps to cure these coatings. UV coating provides greater protection and reflective properties than varnish and aqueous, with gloss and dull sheens available. Fingerprinting can become more apparent on sheets printed with gloss UV when over a large dark solid print coverage.