Experts Discuss State of Inkjet Printing Paper Market: What, Why and How Much
By Patrick Henry, Senior Editor at NAPCO Media
It's a misconception to assume that just because a paper has been pretreated, it will work with a given production inkjet printing press unless the press manufacturer has qualified the paper as suitable for its equipment.
Sept. 26, 2018 (Printing Impressions) - With interest in production inkjet printing surging across all sectors of the industry, it's a good idea to take stock (pun intended) of the substrates that will — and in some cases will not — work with the process.
Paper is paper, and making sheets and rolls for production inkjet presses isn't radically different from making them for conventional equipment. Where the two types part company is in their respective interactions with machines and ink: a distinction that has given rise to new types of inkjet papers and a better understanding of how to print successfully with them.
Before there were inkjet papers, there were offset papers, and running the latter on inkjet presses is sometimes possible — but seldom with top-quality results.
Spraying low-viscosity, water-based inkjet ink onto the “naked freesheet” most uncoated offset paper consists of can be compared to “putting colored water on a sponge,” points out Mary Schilling, president of Schilling Inkjet Consulting. Fibers that are unable to “grasp the pigment” leave little of it on the surface of the sheet, reducing reflectivity and compromising the appearance of color.
The opposite problem arises with coated offset papers, which are too non-porous to allow the proper amount of inkjet ink absorption to occur. This, according to Marco Boer, VP of IT Strategies and conference chair of the annual Inkjet Summit, is an “unintended consequence” of using coatings to make up for the shortcomings of the less expensive pulps that paper manufacturers have sometimes resorted to in order to save money.
Offset stocks and inkjet inks can grow friendlier with the help of pretreatment fluids applied to the surface of the paper before printing. The fluids, which essentially are saline solutions, improve pigment holdout and aid drying.
When they're correctly matched with the ink, says David Zwang, principal consultant of Zwang & Co., “they work really well” — and not only on offset papers. He recently saw a hybrid flexo/inkjet application in which a binding agent laid down before the ink made it possible to jet successfully onto plastic.
Nevertheless, Zwang adds, it's a misconception to assume that just because a paper has been pretreated, it will work with a given production inkjet printing press unless the press manufacturer has qualified the paper as suitable for its equipment.
“There is still a lot of art to this,” Boer insists, noting that while pretreatment fluids are mostly similar, the porosities and surface tensions of the papers they're applied to can vary considerably.
Paging Duncan Hines?
Papers manufactured specifically as inkjet grades are either treated or coated with substances that make them better at catching and holding jetted pigments. Treating puts the additives “on the cake batter,” as Schilling describes the wet pulp slurry of papermaking, during the manufacturing sequence. Coating introduces the additives separately, after the paper is fully formed.
There's a tradeoff of price and quality between the two methods, with treated papers being more economical (because providing the additives doesn't require an extra manufacturing step) and coated papers superior in printed appearance (because the coating helps the pigment to stand out higher on the surface).
Another way to make paper inkjet-compatible is to . . . go to the full story on Printing Impressions' website: www.piworld.com/article/inkjet-printing-paper-market-what-why-and-how-much
SOURCE: Printing Impressions