UV-curable ink is cured almost instantly by UV light as it is printed. Rather than soaking into the media or relying on solvent to evaporate, it forms a hardened layer that sits on top of the surface. That is why UV printers can print directly onto rigid boards, acrylic, glass, wood and many other materials, and why their output is usually ready to handle as soon as it leaves the bed.
Does a UV print need protecting?
Often it is tough enough as it is. But there are good reasons to add a protective layer:
- Cured UV ink can be relatively brittle on some media and may scratch, chip or crack at edges and folds.
- Prints in public spaces, on counters or on floors can face constant abrasion and cleaning.
- A coating can even out the surface, since UV ink can leave a slightly textured or variable sheen, particularly where ink is layered.
- Additional UV inhibitors help where prints are in strong sunlight for long periods.
The adhesion question
Because cured UV ink forms a hard, closed surface, the challenge with coating is less about reaction and more about bonding. A coating needs something to grip. Adhesion can vary with the ink set, how fully the ink was cured, whether a gloss or matte print mode was used, and the media underneath. Unprinted areas of the substrate may also behave differently from printed areas.
Under-cured ink is worth ruling out first. If the lamps were running low or the print speed was high, the surface may not have cured fully, and a coating can make that worse rather than better.
A sensible process
- Make sure the print is fully cured and the surface is clean, dry and free from dust or handling marks.
- Test Colourjet on a printed offcut, including both inked and bare substrate areas.
- Once the coating is dry, check adhesion with a cross-hatch or tape test, and look closely at edges.
- For flexible UV prints, bend or roll the sample to see whether the coating and ink move together.
For rigid UV prints, a flatbed laminator such as the Kala Applikator can be a practical way to apply protection evenly. Roll-to-roll UV work suits a liquid lamination machine. Both are on our equipment page, and the coatings section explains the coating itself.
Phototex on UV printers
Phototex is compatible with UV printers, which makes it an option for removable wall graphics produced on a roll-fed UV machine. Check that your printer handles a fabric media of this kind and that the cured ink stays flexible enough for application.
If you are not sure how a coating will bond to your UV prints, send us a cured sample and we will advise, or pick up the phone on 01252 624 411.