Printers have known for a long time that some aqueous coatings make an excellent primer for offline UV jobs, but more and more “specialty” jobs require foil stamping, gluing [pocket folders], ink jet [address labels], or the ability to go through a laser printer.
Ultraviolet [UV] Coating
Almost every high-end commercial printer sends a few jobs out to an offline UV printer. While some inks are receptive to UV coating, many are not; and it is impractical to inventory and switch inks for the occasional UV job. A select number of aqueous coatings can be used as UV primer. Printers who use these aqueous coatings can use their normal inks to print a job. Not all aqueous coatings work for this application. Talk to your coating representative to make sure the coating you are using can be used as a UV primer. In most cases, it is a good idea to qualify your aqueous coating, ink, and UV coating as a package.
Useful advice : If the aqueous coating was designed as a UV primer, simply allow the job to sit for 24 to 48 hours. This will allow the ink solvents to volatilize from the sheet, thus improving adhesion.
Many aqueous coatings are foil-stampable. Check with your aqueous coating representative for coatings that are receptive to foil stamping. Again, it is wise to qualify the ink, coating and foil stamp as a package.
Some printers choose not to “spare out” an area for ink jetting address labels. Usually, water-based ink jets will not penetrate the aqueous coating surface and will smudge. Alcohol-based ink jet usually works well for this application.
Most aqueous coatings will not re-melt when subjected to a laser printer. In addition, most laser printer inks will not absorb through the aqueous coating and will eventually flake off.
Ink Over Coating
Occasionally, a printer may choose to print the same side of a sheet twice, inking atop aqueous coating. While not impossible, it is difficult. Ink applied over coating cannot absorb into the sheet and will remain wet for a much longer time. Extra precautions to avoid offsetting should be taken including running small loads and using spray powder.