Color matching in flexography is complex, with numerous combinations of substrate, ink set and anilox count all affecting the result.
To deliver repeatable quality and protect margins, it’s necessary to standardize the workflow with digital color references, measurements and databases for fast and easy recall.
For the flexographic printer, color matching is perhaps the most complex element of the prepress workflow. Label and packaging web converters are losing valuable production hours and scrapping material in attempting to meet tight color targets expected by brands for their packaging media.
All photos courtesy of Flint Group
Brand owners’ concern about color quality was a consequence of the importance of point-of-sale presentation. As far as choice is concerned, the American consumer has never had it so good: an average supermarket has in excess of 40,000 SKUs—about a six-fold increase in the last 20 years. Even in the internet age, the retail shelf is where the majority of buying decisions are made, and brands must compete fiercely for just a few fleeting seconds of the passing consumer’s attention.
Color is an important element of a brand’s strong visual identity for its role in creating perceptions. According to London-based design agency Reboot Online, color can increase brand recognition by up to 80 percent. Even without the logo, consumers can distinguish a brand from its color alone–Ikea blue-yellow; Starbucks green-white; Coca-Cola red and so on.
Because of this, brand owners develop unique colors to distinguish themselves. Indeed, the lengths they will go to, to legally protect their exclusive use—as evidenced by the Cadbury—gives you an idea of the value attributed to a special hue. Unsurprisingly, brands expect their packaging suppliers to deliver it with consistent precision, on all substrates, often to within 1.5 Delta E—and not meeting this standard is reason enough for contract terminations.
Flexographic printers rely on pre-mixed “spot colors,” based on a special recipe of base colors and additives, to reproduce these with stability. Today, not only are colors hard to get right, there are more of them to mix, too: Consider the variety of flavors, scents, health-conscious options, regional sub-brands and temporary promotions a brand may have. As a result, converters need new matches for as many as half their color mixing jobs per day.
Color Matching Trial & Error
In a survey of US and European label converters that Flint Group conducted in 2016, color matching was considered the main hindrance to productivity—way ahead of other challenges like viscosity or curing. Operators were losing, on average, two-and-a-half press hours per day trying to reach color targets. This was a disturbing figure that merited further inquiry.
We discovered the methods used were at the root of lost value—the classic “trial-and-error” color matching method. On receiving a printing order, the press operator consulted the Pantone formula guide, which provides the recipe for each shade, then mixed the base colors and additives accordingly. They would then use eyesight to compare the accuracy of the mix to the Pantone shade.
Variables Affecting Color
There are significant flaws with this approach. Number one, using the naked eye is subjective, as everyone sees color differently, according to genetic factors and levels of alertness. Number two, the formula guide provides variations for only coated and uncoated papers. This may be ideal for sheetfed offset printers, but no good for label and packaging printers, and especially those printing with flexography. The type of substrates used, ink chemistry and anilox cell count all influence the final color result, and given the multitude of substrates and complementary print processes used by flexographic printers today, adaptations to the Pantone recipes are inevitable.
The properties, color and surface treatment of the substrate all cause a variation in the reflection and absorption of light. Choice of anilox roll also has a significant influence on color quality because higher anilox cell volumes mean a larger ink transfer and thus greater color density. Suppose, for instance, the identical spot color is required for a logo with flood-coated opaque on a front label, and fine text on the back. Different anilox cell volumes will be used to create these effects. It means a different recipe is therefore needed, to get consistent results when reproducing a single graphic design on different substrates—or even different labels on the same pack.
The example of a label converter supplying the drinks industry in Poland illustrates the challenge. The company performs 15 color matches when supplying bottle labels for a leading vodka brand: each of its five flavors featured a distinctive color shade, which needs a different formulation for each of the bottle’s three labels. While the front label’s vivid graphics capture attention, the back used a high anilox cell count to reproduce small text, and the neck substrate was silver instead of white.
For these reasons, color matching was a haphazard process. Recipes were rarely accurate on the first attempt, resulting in ink waste and significant scrap material. There was low probability of getting the same results for repeat orders. Matching accuracy differed from one operator to the next, making color consistency almost impossible. It took experience to adapt a generic Pantone formula to the application, and some employees have a better eye for color than others. So, a problem emerges of designating a color matcher on each shift.
The extent of lost revenue due to inefficient matching becomes clear when multiplying the number of hours’ idle time by the hourly rate for press time. In folding carton and flexible packaging printing, with higher output and press speeds as fast as 2,000 fpm, that loss is leveraged.
Measurable, Repeatable Science
Making color matching a controlled, measurable and repeatable process requires a number of essential elements. Everyone involved in specifying, printing and approving color must use and communicate color values with recognized digital references. Examples include L*a*b* values, which give coordinates for lightness, green-red and blue-yellow, as well as CxF files, allowing all aspects of a color to be communicated across the supply chain.
Another element is automation, reducing human input where possible. Equipment for achieving this may include a spectrophotometer to digitally measure color and ink dispensing systems to automatically dispense shades in exact amounts for the printing job.
But without a means of formulating the color that takes into account all influencing factors, the printer faces delay in color matching even with these installed. This led to the creation of remedies like VIVO Colour Solutions, an intelligent cloud-based database of color and mixing recipes that covers any combination of printing method, ink type and printing media.
The database translates the customer’s color target into an ink formulation to match the color target on the press, taking into account the substrate, ink set and anilox, to ensure accuracy at the opening attempt.
The database is very easy to use: the technician enters the color target with digital references noted previously. If these are not known, the database can compute digital references from a scan of a color sample with a spectrophotometer. The user then searches for and selects the required ink type, substrate and anilox cell count, and almost instantly, the database provides the correct ink formulation, which may be printed out. The database can link up with software from ink logistics providers, enabling automatic communication of the ink formulation to the ink dispenser for automatic mixing.
Cloud-Based Color Database
By necessity, the database is a bespoke service for each customer, fine-tuned to the conditions of the client’s press. When a converter signs up for a user license, a fingerprint of the press is conducted, and all anilox rolls used for each job are audited, to create a tailored search engine.
Database license holders access the entire color database through a secure search engine in the cloud, as well as a web portal service for support and new color enquiries.
As of June of this year, the database contains approximately 350,000 UV flexographic formulas, all tested at Flint’s Global Colour Centre, combined from around 2,000 color shades, currently made using seven ink series, seven anilox film weights and a variety of substrate types. Shortly, the database will also host water-based flexographic ink, UV offset and UV screen inks.
Support On Demand
Complementing the database is a web portal, providing an interactive service, through which customers can request new formulations (for example, on a previously untested substrate), which are supplied within 24 hours.
Using a database and commonly accepted color standards, simplifies and accelerates the once-complex process of color matching, potentially generating value worth more than $100,000 per year.
Consistent Quality
This gives consistently accurate results, covering the complete visible color spectrum at the initial attempt, irrespective of who is matching the color—or where. The converter has assurance that the most complex brand colors will be faithfully reproduced on target on the press, from one shift to the next, and crucially, for multi-national printing houses—one location to the next. When the repeat order comes, identical results are similarly assured.
Getting quality “right the first time” leads to significant material savings, improving ink yield and eliminating up to 1,000+ sq. ft. of startup waste per job. Consider also the productivity boost made possible by generating ink recipes in just a fraction of the time taken by conventional matching with the Pantone book. The value gained by two-and-one-half hours of extra machine uptime will only increase as new presses arrive on the market capable of greater quality and faster speeds.
Taking the need for human expertise out of color matching should also be welcome news for the operators concerned. It breaks the organizational silo and frees up valuable time that can be spent preparing for a smoother, faster job changeover, or creatively exploring new opportunities for leaner and smarter production.
The recipe database, therefore, is an important complement to an automated color-matching system.
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