Process Control Is Key to Effective Ink Optimization

One of the keys to efficient package printing is understanding the source of unwanted color variation and implementing measures to drive those deviations out of the process.

In point of fact, says Marc Welch, vice president of sales for GMG (www.gmgcolor.com), "Smart printers have been doing this for years. What's driving the current focus on ink optimization in the packaging market is that people are beginning to look closely at ways to decrease color variation and increase the color consistency of products on the shelf."

However, he observed, the full value of an ink optimization solution is best realized where appropriate process controls have been implemented to ensure that press, proof, incoming files, and CtP curves are properly aligned to a given specification (target, densities, dot gain value, etc.).

Maintaining consistent image color during a press run typically starts in prepress and involves evaluating the color separation process, taking into account the ink, ink properties, substrate characteristics, and press condition. "Over the past five years or so, we've become more aware of the problem and have started to detect and measure color inconsistencies and to nail down a number of troublesome variables," Welch said.

Eliminating film-based workflows in favor of computer-to-plate has helped, but problems persist. The difficulty is especially acute in folding carton production, where the color inconsistency is rooted in super-high-density ink coverage.

By the numbers

According to Welch, problems stem from a fundamental disconnect between the prepress activity involved in creating the file and the needs of the package end-user. Especially troubling, he said, are "generic CMYK separations" that fail to take into account the type of press, ink, ink properties, substrate, and overprint characteristics associated with the job.

To a large extent and despite the adoption of digital workflows, he says, "We're still stuck in film concepts." That is, "When prepress companies made the color separations and proofed from film, and shipped both film and proofs to the printer, the press would be made to match the analog proof. We now substitute a 1-bit data file for each color and ship a 'locked-down' digital file to the printer without tuning the file to the press. We need to get away from 1-bit workflows," Welch explains.

In digital workflows, calibration in prepress is defined by how the press prints. Regardless of the specification in question (flexo's FIRST is a good example), printing "to the numbers" will result in more consistent color—but only if operators follow the specification closely from job to job, shift to shift, and day to day, using the appropriate measurement devices and other tools.

There's more to ink optimization than reducing the amount of ink that is used, Welch insists. "Color management on the back end is a prerequisite to deriving the full benefit of ink optimization. You need to characterize the press, set up a standard, and understand what the press wants to do."

"Consumer product companies would love to have more and better process controls," Welch says, "but, in order to achieve it, more education, adjustment, and measurement need to take place—and everybody needs to sign up." pP

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