Many commercial printers have purchased a digital press and a UV offline coating unit in order to provide their customers with printed pieces with an aesthetically pleasing coating. However, printers are often surprised at the difficulty they encounter when trying to lay down a smooth coating film over certain hard-to-coat digital inks. The problem may present itself as poor adhesion (easily scratching or scuffing) or as reticulation (where the ink actually beads-up and doesn’t lay smoothly over the surface of the ink). These problems are especially evident in heavy black or dark solid colors.

The problem

Many digital presses use ink that contains oil or other additives that can migrate to the surface—even after the ink feels dry—and prevent the coating from adhering properly.

The solution

Fortunately, all is not lost. Here are three tips to help you coat over these sometimes difficult digital inks.

Tip #1: IR drying

Although the infrared drying feature on coating equipment has many uses, mostly related to drying aqueous or solvent-based inks and coatings, many operators don’t think about IR when working with UV digital ink—which cures under UV light and not by infrared or heat drying. In the case of these inks where oils or additives have migrated to the surface, a quick pass under the IR dryers can flash off some of the offending material and allow more of the coating to adhere.

Tip #2: Coat it quickly

Consider applying the coating as soon as possible after completing the print run. The longer the printed pieces sit, the more time the materials in the ink have to migrate to the surface and make coating difficult. Coating and curing over these inks immediately after they come off your press denies the materials in the ink the chance to migrate to the surface where they cause coating problems.

Tip #3 Use a coating designed to be run over Hard-to-Coat Digital Inks

Specialized coatings have been designed to coat over these  hard-to-coat digital inks. Magnum Inks & Coatings®, offers its LithoCoat™ Digital UV line of coatings specifically to overcome this challenge. These coatings give you the ability to lay down a smooth, even film providing that amazing printed piece your customer is looking for.