Production Inkjet Papers

In 1962, economist Fritz Machlup first described a phenomenon called “the half-life of knowledge,” which referred to the time that will elapse before half the knowledge in a particular subject will be proven to be untrue, or at the very least heavily revised. New discoveries, new experiments, and better means of measurement are constantly updating the accumulated knowledge in any given area. Think about how much we know about the planet Pluto compared to this time last year. And, closer to home, if you have ever tried to keep up with what foods are really good for you, you know what I mean.

The idea of the half-life of knowledge is certainly applicable to production inkjet printing. “Customers still cling to what they knew a few years ago,” said John Crumbaugh, Media & Ink Product Marketing Manager for Canon Solutions America (CSA). Given the long buying cycles common to press investment—12 to 18 months—so much change takes place that something that was true at the beginning of the sales cycle may no longer be true by the time they actually buy the press, and there may be a paper available that wasn’t when they started their inquiries. “The industry is moving faster than the customer,” said Crumbaugh,

Crumbaugh says that inkjet equipment manufacturers like CSA are fighting the conventional wisdom that may have been true a few years ago—there are so few inkjet-compatible papers available—that the technology is not suitable for any but a narrow range of applications and markets, such as transactional or book printing.

“The last 12 to 18 months in the world of inkjet has been a sea change in terms of ink and media compatibility,” said Pat McGrew, Print, Inkjet, and Production Mail Evangelist for HP. HP has recently debuted its High Definition Nozzle Architecture (HDNA) technology for its production inkjet presses. “When you compare that to the work that the paper mills have done in bringing amazing papers to market, it’s changed our world quite a bit.”

The Paper Problem

Let’s back up for a second and recap the story so far. Much of the industry’s—for want of a better word—“infrastructure” has been developed over the latter half of the 20th century around offset lithography. Based on the principle—generally—that oil and water don’t mix, the vast majority of the paper available for commercial printing has been optimized for oil-based lithographic inks.

Inkjet, however, uses water-based inks that can be up to 95 percent water, depending on the formulation. Spray even a little bit of water on a regular piece of paper and it’s going to distort at best or come apart at worst. So when you’re running an inkjet press, you’re running a web of paper underneath what can not far-fetchedly be considered a sprinkler system. In any printing technology, ink dries via evaporation and/or absorption into the paper. In inkjet printing, with so much water being involved, the goal is to rely more on the former and less on the latter. So to maximize ink holdout—the extent to which it stays on the surface of the paper and doesn’t penetrate into the fibers—paper needs to be treated in some way. Or, in other words, optimized for inkjet printing.

(Compounding the problem is that inkjet inks can be either dye- or pigment-based; the former uses a liquid colorant suspended in the aqueous ink vehicle while the latter uses a solid colorant. Both these inks can perform quite differently.)

And that’s just uncoated papers. Coated papers can exhibit the opposite problem: too much ink holdout, such that it just beads up and rolls off the surface, like rain on a newly waxed car. So the challenge is to reduce the ink holdout of coated papers so you don’t end up with renegade drops of ink spattering all over the inside of the press.

“Historically the challenge with coated papers, particularly glossy stocks, has been balancing the need to absorb and dry off the high water content of the ink while retaining a true gloss and a vibrant image,” said Ann Whalen, Senior Vice President, Marketing & Customer Services for Appleton Coated.

Initially, production inkjet was in a bit of a chicken-and-egg situation vis-à-vis paper. Mills were reluctant to produce inkjet-optimized grades before there were enough machines in the market, and equipment manufacturers couldn’t get machines in the market unless there were enough papers to cover the range of applications. Happily, the various chickens and eggs have come home to roost (how’s that for a mixed—or perhaps scrambled—metaphor) and the number and variety of papers available that are compatible with production inkjet systems have taken off tremendously.

CSA has found this to be especially the case with cut-sheet inkjet. (CSA launched the VarioPrint i300 cut-sheet inkjet press last year.) “Paper mills are coming up with special papers made specifically for cut-sheet inkjet to feed the i300,” said Crumbaugh. “A lot more commercial grades have come on the scene in the past few months because there’s a larger selection of paper in the cut-sheet world in the first place. We have everything from gloss inkjet coated down to literally copy paper and everything in between: matte coateds, lightweights, heavyweights.”

That said, there are still some holes in the range of papers available. “There is little availability of affordable glossy products for dye-based systems,” said Whalen. “In addition, there are still drying challenges in running glossy coated papers with pigment inks on some of the high-speed inkjet technology platforms.”

Trick or Treat?

Early on in the life of inkjet, there was much talk about treated paper to improve runnability. What is the status of treated paper today? “You pay more for a treated inkjet sheet, even though those prices have dropped,” said Crumbaugh. “So there is a desire on the part of customers to print on the same products they have been printing on all along, and they can in many many cases.” However, he is quick to add a caveat: “For the appropriate work,” he said. “If someone is printing black-and-white trade books, they certainly don’t need a treated sheet. But if they’re going to print marketing and promotional work, they’re going to want a treated sheet. People say you can save all this money by not using treated sheets, and that’s true, but the question is, can you actually sell the job?”

Treated inkjet papers are still specialty papers for paper mills, and they are made under very tight tolerances, so they’re very consistent. “More than anything else, what you buy with a treated sheet is color,” said Crumbaugh. “The other thing you buy is stability.”

Again, this is something that is best evaluated on a job-by-job basis.

As an alternative to using treated paper, last year HP introduced a precoating/priming unit for its production inkjet web presses. “When you pair that with our bonding agent technology, you have multiple ways you might create a better medium for the ink to land on,” said McGrew. Again, though, whether or not to use these processes will be a function of the specific media you’re using and the job for which you’re using it. “Priming is good for offset coated stock and for printing on lighter-weight media,” said McGrew. “The higher [ink] coverage you want, the more likely you’d want to use a priming agent.”

Testing…Testing…

The good news is that printing equipment manufacturers have done most of the heavy lifting in terms of determining what and how well papers will run on their equipment. Crumbaugh runs CSA’s Media Lab which extensively tests papers and provides a database of papers for CSA customers that indicates how different papers perform on CSA’s inkjet equipment. HP has a Media Locator available to its users that also serves as a database of compatible media, and also suggests what color profiles, dryer settings, and print speeds are optimal for a given paper. It also indicates whether it’s a paper that would benefit from a bonding or priming solution or other kind of treatment.

Speaking of color profiling, once upon a time color profiling was the “secret sauce” to getting optimal quality out of an inkjet press and while that is still largely true, it is not the arcane process it used to be. “It’s kind of ‘set it and forget it’ in a way,” said Crumbaugh. At this point, “it shouldn’t be challenge. It’s less important than it used to be in that you shouldn’t be chasing color. Inkjet is as stable as your paper is, and is very reliable. If you’re using a good paper, if you’ve color-managed it once, you really don’t have to chase it that much.”

Still, said McGrew, “Color profiling is the differentiator. It can be the key to producing absolutely rock solid, amazing work vs. run-of-the-mill work that anyone can produce.”

Too Many Papers, Not Enough Time

As drupa approaches, it’s a safe bet there will be a host of new production inkjet introductions, and as the equipment options expand, the paper options will expand accordingly. One trend Crumbaugh sees gaining traction is what we might call “multi-platform paper.” “We’re going to see more and more mainstream papers coming out with an inkjet version, so customers can move from an offset job to an inkjet job to a toner job and use the same branding,” he said.

Appleton Coated has also been moving in this direction. “In addition to the standard uncoated offset products, we’ve expanded our offering for uncoated inkjet products to include both a 100-percent post-consumer recycled fiber offset and a lightweight Pharma Insert Opaque sheet suitable for dye-based or pigment-based inkjet printing systems,” said Whalen.

So the old conventional wisdom that inkjet users are severely limited in their choice of papers is no longer conventional—nor even wisdom.

“Today it would be very hard to find a paper you couldn’t run,” said McGrew. “That was not our story five years ago. The mills are constantly bringing new papers to market.” And even if certain media have not been tested, certified, or optimized, “It’s pretty easy to figure out what you need to know to print on them,” said McGrew.

“The whole point is to make sure our customers have as many papers as possible,” said Crumbaugh. “We’re in a super-exciting period of time from an equipment standpoint—and from a paper standpoint.”