Pumped-Up Inks Put to Tests

by Andrew Bowser

As part of an effort to improve print quality, some newspapers are checking out inks that are significantly stronger than the Ad-Litho standard.

Managers at The Plain Dealer in Cleveland report that recent tests of cyan and magenta inks 50 percent stronger than the Ad-Litho standard produced ink-curve reductions of 20 percent; using an ink 100 percent stronger than Ad-Litho reduced the ink curve by 40 percent.

The end result: reduced off-setting and a cleaner look in four-color process, says Bill Moore, director of operations. A higher-strength black produced similar results.

Moore reports improved mileage, but because high-strength inks cost more than normal inks, it won't be clear if they saved any money until he compares full-year 1996 and 1995 ink bills.

In April, the Chicago Tribune switched to high-strength cyan, magenta, and yellow inks with a pigment ratio 50 percent higher than the standard Ad-Litho formula. Paul Lynch, manager of quality and technical training, says he hopes a higher-pigmented ink will improve quality.

Even after four months, press operators at the Tribune found it challenging to optimize ink and water curves to account for the new ink's higher-intensity appearance. Ink mileage and showthrough have improved, the former by 18 to 21 percent, but no measurable difference has been seen in dot gain, setoff and print contrast. There's been a "very slight" improvement in color trapping, Lynch adds, but "we have not seen a widening of the gamut."

The Los Angeles Times recently tried nine different black inks, six of them high-density formula produced by Flint Ink, which introduced high-density brands this April. The Times will further test a high-strength ink with a pigment concentration higher than industry standards because it showed the best print-quality attributes.

The ink yielded a film thickness of 0.7 g/m2 (compared with its usual 0.9 g/m2) at a density level of 1.05 when tested on a Prüfbau test press, according to Niko Ruokosuo, process control and print quality manager. But press operators at the Times found the highest-density ink caused mottling and flecking on the paper toward the end of a press run.

"My guess is, with stronger inks, the film becomes thinner and more sensitive to any fibers and fillers from the paper that get into the rollers," Ruokosuo says.

Modifying the ink formula's viscosity achieved an ink-film thickness of 0.8 g/m2. Initial testing indicates that this modified ink lays down better.

Using higher-strength inks, the Times has seen lower dot-gain values, better print contrast and less showthrough. It appears the new ink will improve mileage by approximately 10 to 12 percent. "We are now comparing mileage to the ink cost and look forward to cost savings," Ruokosuo says.

Andrew Bowser is a freelance writer based in New Orleans. E-mail, andyb@comm.net; phone (504) 897-4026; fax, (504) 899-9140.