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Narrow Web Gravure



An ancient print process enjoys a small revival among high end narrow web converters.



By Jack Kenny



Published July 20, 2005
Related Searches: Rotary screen Hot foil UV flexo
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Rotogravure printing has been around for over a hundred years. It is said to have been developed in 1878 by a Czech by the name of Karl Klic (also spelled Klietsch), who kept his idea secret until it was stolen and brought to the United States in 1903. In the narrow web industry, gravure has remained something of a secret, and for several reasons: Few companies have manufactured narrow web gravure equipment, some misconceptions exist among printers about the process, and those who do use gravure would rather not discuss it.

For years gravure has been looked at askance by some flexo printers and others in the narrow web field as too expensive, too dangerous (considering the prominence of solvent based inks used in the process), and good only for long runs.

But gravure is run by some of the more well known narrow web printers — among them Sancoa, National Label, CCL, Seal-It, Spear — and is being discussed more often at conferences and exhibitions. What is it about Klic's little secret?

For years, the familiar name in narrow web gravure is Chesnut Engineering, which makes presses. Richard Chesnut, founder and president, is still at it in Fairfield, NJ, and is enjoying the newfound interest in his favorite print process. "It's the next step," he says. "Every 10 years the industry would jump into something new. In the 1960s it was flexo, and in the '70s it was rotary letterpress. Then came UV flexo, then rotary screen. Now gravure is the thing people are talking about.

"You can argue that the gravure dot is finer than a flexo dot, but I say yes, you can get quality with all the print processes. But with gravure you're talking shiny metallics and four color process, and it gets a lot easier at a lower cost. That's why there is an interest in it."


Metallics, indeed. The talk on the street is that the big product marketers, everyone's favorite label end users, want shiny, want metallic, and want it now. "The push for gravure is very much driven by the high end label market, the Procter & Gambles, the Palmolives, the blue chip companies. Their objective is to get gold or silver effect on their labels without paying so much for it." That's Jakob Landberg, sales director for Nilpeter, in Slagelse, Denmark. Nilpeter started making gravure cassettes for certain of its narrow web presses in 2001.

Nilpeter's gravure print station

Dense metallics

Rotogravure is perhaps the simplest of all rotary printing processes, requiring the least number of elements to transfer ink to the substrate. A metal cylinder carrying the print image (engraved in reverse) picks up the ink from the reservoir. Excess ink is removed with a doctor blade. The cylinder turns and transfers the ink directly to the paper or film. The ink is then dried.

One advantage of gravure is that the laydown of ink is heavier than all processes with the exception of screen printing. "Gravure can lay down a lot of ink," says Ed Dedman, market development manager for SICPA North America, a ink manufacturer with headquarters in Brooklyn Park, MN. "The trade-off with gravure is that if you want to lay down heavy ink film, you can't have a lot of detail in your engraving. If you want fine type and opacity, you can get either, but not both. So in gravure the key is the engraving — the number of lines per inch, the volume it will carry, the depth — all of those come into play. You can make a gravure engraving that will put down a tremendous ink thickness, but you're just flooding the ink to the substrate."

A dense layer of metallic gold or silver comes close to the look of actual metal foil. The same goes for fluorescents. "Where gravure shines is when you're trying to lay down metallic and fluorescent inks, because those inks have larger particles, which both flexo and offset have a difficult time laying down," says Frank Gerace, president of Multi-Color Corporation. Multi-Color is a Cincinnati based printer and converter of a wide range of labels using gravure, flexo and offset processes.

"First you have to look at the cost of foil versus the cost of ink," observes Nilpeter's Landberg. "Second, if you run foil you reduce the process speed, and you raise the tooling costs. If you really want gold today, hot foil is best, but in a spot gravure does the job beautifully." The call for gravure, he adds, is for products in the health and beauty markets.

Nilpeter recently performed a retrofit of a customer's press to install three gravure stations, all in a row, for the printing of cigarette cartons. "In metallic ink, small metal flakes are diluted into a solvent," Landberg says, "and to get a mirror effect you have to have the flakes oriented in the same direction. That's difficult to achieve. But if you print a metallic color two or three times on top of each other, you get almost the same effect. Our customers are doing that using an inexpensive carton."

The best metallic inks are solvent based, industry experts agree, because the metallic components perform much better in that medium. "And solvent based inks can give you much better adhesion on films," says Dedman.

Converters who are exploring the uses of gravure to make labels in most cases are using the process to lay down the heavy metallic layer, or a dense opaque white, then printing images and text in colors on top; or if the job is reverse printed, the gravure ink will go last. Nilpeter's gravure station is moveable: It's a cassette that can be moved to any spot in the press, as can the accompanying electric dryer oven located above the unit. Jakob Landberg notes that all of the presses Nilpeter has fitted with gravure stations are offset, with the exception of one flexographic press.


Ink developments
One of the holy grails in the gravure industry is UV ink. Chemists have been working on it for years, and only now are coming close. "What we have tried to focus on is to get a gravure white that can be used instead of screen ink, to be able to achieve a high-built, very, very opaque white without slowing down the press," says Landberg.

Nilpeter has been working with Akzo Nobel Inks on the development of UV gravure inks. "The biggest problem with UV in gravure has been the rheology," says Mike Buystedt, director of market development for Akzo Nobel Inks, Plymouth, MN. Rheology is defined as the study of the deformation and flow of matter. "In the past the raw materials were not available to give the viscosity needed for gravure. And there are still technical issues we're working through.

"The doctor blade in any gravure process always leaves a little residual ink on the cylinder in the non-image area, a very thin layer. When water or solvent based inks are used, that ink dries even before it hits the substrate you're printing on. With UV inks, however, you have a risk with that residual ink transferring because UV ink doesn't dry."

Akzo Nobel is still at work on the project, resolving viscosity and other issues. "Gravure gives you the opportunity to rival screen printing with a faster print process," Buystedt says. "You can get brilliant colors with lots of ink."

SICPA produces energy curable gravure coatings, which are clear, and according to Dedman the company is at work on a UV curable opaque white. "The viscosity has to be low, so it's harder to make up a functional electron beam or UV curable product and get much pigment loading to maintain that viscosity," he notes. "You start adding pigment and the viscosity wants to go up because you're adding thicker materials. Solvent based for gravure is by far the preferred ink today. You get far more wetting power and pigment based power."

According to Dedman, differences in mindset exist between flexo and gravure printers. One is the mixing of inks and the terminology used to define them. "The other mindset difference is that traditionally in narrow web the operator will shake up a jug of ink, screw off the top, pour it in and it's ready to go.

"Gravure's solvent based inks come in non-press-ready form. You make a solvent blend that is based on press speed, the substrate and the press configuration, and you add solvents to that ink to reduce it to the viscosity you want for that job. It's a big learning curve to get press operators to understand, and it's been a challenge."


Economies

"An inline gravure press should cost no more than an inline flexo press, because it's no more complex than a flexo press, even less so," says Tim Napier, owner of CNW Inc., of Cincinnati, a prepress and engraving company. Napier argues one of the issues about gravure, that it's expensive. "Most printers who do narrow web gravure pretty much charge more because they can." He adds that he is in the process of talking with people in the industry about the manufacture of a new line of narrow gravure presses at affordable prices. "In India they build 10-color presses for $50,000. They don't look like much, but they get the job done. The first narrow web guy who goes out and puts gravure in at the cost of flexo is going to corner the market."

An advantage that gravure brings is cylinder longevity. Because it's metal, it doesn't wear out like a flexo plate. "There's no waste," says Napier. "There's no company selling a lot of material that has to be imaged repeatedly. It's just copper, and such a little volume of it."

Gravure print cylinder cost has always been an issue, because the traditional cylinder is solid steel, coated with copper, engraved using specialty equipment, and coated with chrome.

"It's also transportation," says Harry McKay, sales and marketing manager for Stork Rotaform, Charlotte, NC. "It costs a lot of money to move a 400 pound cylinder between point A and point B." One solution to that cost is the gravure print sleeve, which Stork Rotaform makes.

"The sleeve works the same way as it does in flexo: You put it on and off of an air mandrel. The sleeve has a nickel base of seven thousandths of an inch thickness, and a flash of bonding copper on top of that, bringing the thickness to 0.008". Then it goes to a plater or engraver who adds a copper layer to it about 0.0055" thick, engraves the image and finishes it with a layer of chrome about a half-thousandth of an inch thick. The total thickness of the finished sleeve is 0.014"."

There's no difference in the image produced by the sleeve or a solid cylinder, McCoy says, and there's no difference in the cylinder's longevity. "The printer is still working with his old friends, copper and chrome. All we suggest is that instead of managing a heavy cylinder, they manage only the important part, which is two pounds."

The sleeves cost much less than a solid cylinder, and shipping them is also much less of an expense. They also save on warehouse space because they can be stacked easily in boxes one atop the other instead of in steel racks. They can also be de-chromed and re-chromed, McCoy adds.

"We'll see more and more gravure in the future," says Denny McGee, sales manager for Mark Andy/Comco, Chesterfield, MO. The Comco division also produces gravure stations for its presses, he says, which will be used for printing of packaging cases.


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