Getting up to Color

Color is one of the most complex aspects of any type of printing, at times seemingly bordering on magic. Yet, it is really a science that operates under very specific rules. Unfortunately, when it comes to putting colors on a substrate and having them live up to the expectations of paying customers, a host of variables come into play, making understanding the science an important part of success.

The CMYK color space (or gamut) covers only a fraction of what our eyes can see. This is acceptable for many needs, but not when printing special shades of pre-mixed inks, such as those of the Pantone Matching System (PMS). Beloved of brand owners, PMS colors, along with other special custom hues, are considered critical to brand integrity and are required on most branded items. The problem is that cyan, magenta, yellow and black can simulate only about 60 percent of the Pantone color library, with some sources limiting it to just 45 percent. Whatever the number, it is insufficient to satisfy brand owners who insist that a certain red, blue or orange is drop dead critical to their brand's success. So it's time to expand the gamut.

The time-honored point-and-shoot method of expansion is to create all the non-critical colors with CMYK, then put spot colors (PMS or custom) on separate inking stations on a press as needed. This works well, but adds costs, limits flexibility, and increases changeover times between jobs requiring a different color palette.

Flexible expansion

The other option is expanding the CMYK gamut with additional colors—commonly orange, green and violet (or blue)—that can be mixed as needed to create spot colors. While somewhat more complex, this offers greater flexibility and can significantly lower clean-up and changeover costs while delivering more vibrant colors and matching up to 90 percent of the Pantone library and many spot colors. The difference shows up even on test runs: a test strip made with just CMYK appears washed out compared to the vivid colors of expanded gamut (EG). The difference comes from the greater saturation of colors produced by overlapping EG colors, even though the amount of each color applied is less than it would be using only four colors. In some instances, flexo presses can be set up to lay down inks in different sequences, such as Yellow-Orange-Magenta-Green-Cyan-Violet-Black. This can provide higher chroma (brightness) and stronger color saturation than a conventional sequence.

On a flexo press set up for EG the seven primary colors, cyan, magenta, yellow and black, plus specific orange, green and violet (or blue) inks stay in the press, even though not all colors are needed for every job. This makes them available to build spot colors and graphics based on each job's requirements, allowing converters to more easily match brand colors without the cost and production overhead of spot color printing. With all inks staying on press, time for wash-ups, make-ready, and downtime can be cut dramatically because the time associated with changing inks, washdown and cleaning is largely eliminated.

Enabling all this upstream of the press is software, such as Esko's Equinox, that lets converters standardize their presses on 5, 6 or 7 inks, thereby limiting some changeovers to just swapping printing plates. The software enables prepress staff to convert CMYK files to ones with expanded gamut profiles, deferring to human judgment for optimal adjustment and approvals. Still, each press should be characterized to help control variables such as which anilox rollers are used, the substrates a job requires, ink densities, plates, and more. And that requires training.

Back to school

Long-time flexo press maker Nilpeter recently held a training session at its Cincinnati, Ohio Technology Center to train press operators on how to take advantage of expanded gamut on the company's FB-3 flexographic press along with features that facilitate short changeover and makeready times. "Our partners [Actega, Esko, Flexografix, Harper, and Tesa] gave in-depth presentations that provided attendees with the knowledge to help them explore deeper into the world of expanded gamut," noted Chris Baldwin, Technology Center Manager at Nilpeter.

"Such training is essential," agrees John Howard, Vice President of Research and Development at Mark Andy. "It can come from press vendors, prepress houses, or by sending press operators to an extended gamut printing class at Clemson University."

The message is clear: expanded gamut adds significant value—and learning how to get the most out of it is worth the investment.

Driven by digital

Key drivers behind the expanded gamut movement are the demand for more vivid colors on labels and flexible packaging and the need for brand-critical colors. The pot is further stirred by the ability of some digital presses, notably HP Indigos, to offer six and seven colors as standard equipment, plus white and silver, as well as the availability of on-press and off-press options purported to match up to 97 percent of the Pantone color range.

Digital press advocates claim it is easier to use an extended gamut on a digital press. This is largely true, and points to a shift in who does the heavy lifting of getting colors right. On an analog press, the craftsmanship of the press operator is critical to having a job print correctly, and often makes all the difference in its success. This is even more important with the added inks of expanded gamut printing. In contrast, on digital press jobs it is the designer and prepress people who prepare a file to ensure the job will print as intended. A matter, if you will, of old school craftsmanship versus digital savvy. Both are good ways to employ EG printing.

Another difference comes on press, especially at changeover times. Unless substrates are changed, digital presses feature minimal (if any) slowdowns between jobs, while analog flexo presses must be stopped so a new job can be set up. With modern flexo presses however, this interval is shrinking, and expanded gamut inks are helping.

"The advancements in the flexo process in combination with the ability to hold extremely tight register and perform automatic job recall, mean digital printing has less of an argument against the flexographic printing process," notes Nilpeter's Baldwin.

Nilpeter is not alone. Expanded gamut printing is becoming part of the landscape for flexo presses and some savvy brand owners are adding it to the list of requirements they ask of converters. And with new flexo presses increasingly being shipped with six, eight or more color stations, filling two or three of those with expanded gamut inks —and investing in some hands-on training—would be a sound business decision. pP

To view this issue and past editions of packagePRINTING in a digital format, please click here.