A print that feels dry to the touch is not always ready to coat. Inks from eco-solvent and solvent printers in particular continue to release solvent for some time after printing, a process known as outgassing. Seal the surface too early and that solvent has nowhere to go. Many of the coating faults we are asked about come back to this single step.
What goes wrong when you rush
- Hazing, clouding or a milky look in the coating.
- Small bubbles or blisters forming as trapped solvent escapes.
- Poor adhesion, with the coating or film lifting later.
- A tacky surface that never quite feels right.
- Colour shift or ink softening where the coating reacts with still-wet ink.
With film lamination, trapped solvent can also cause the film to wrinkle, silver or lift at the edges over the following days.
Which prints need most care
Eco-solvent and solvent prints generally need the longest to outgas. Latex prints are cured in the printer but should still be allowed to cool and settle. UV prints are cured instantly by the lamps, although it is still sensible to let them reach room temperature. Aqueous pigment prints on fine art papers and canvas need moisture to leave the media, which can take longer in damp conditions. Always check the ink and media manufacturers’ guidance, because the right time depends on the combination, the ink load and the conditions in your workshop.
How to help prints dry properly
- Avoid rewinding prints tightly straight off the printer. A tight roll traps solvent between layers.
- Where space allows, hang prints or lay them flat with the printed side exposed to air.
- If prints must be rolled, roll loosely with the print side out, or interleave with a clean sheet.
- Keep the drying area ventilated and at a steady, comfortable room temperature. Cold, damp conditions slow drying.
- Use the printer’s dryer or heater settings recommended for the media profile.
- Label prints with the time they came off the printer so everyone knows when they are ready.
Telling when a print is ready
Touch alone is unreliable. A useful habit is to check for any solvent smell close to the surface, and to look at heavy ink areas such as deep shadows and solid colours, as these hold solvent longest. The most dependable method is to coat a test strip from the same print run and inspect it once fully dry. If it looks clear and even, the main job is likely ready too. Our guide to testing a coating on your media explains how to set up that test.
Planning it into production
The simplest fix is to treat drying as a scheduled stage, not an afterthought. Build it into turnaround times you quote, and print coated jobs early in the day or the day before. That way nobody is tempted to coat a print that is not ready because a deadline is looming. For which inks suit our coatings, see the compatibility page.
Seeing hazing or bubbles and not sure whether drying is the cause? Give us a ring on 01252 624 411 or send us a description and photos.