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Getting Your Color Right

By Peggy M. Underwood

April 2, 2018

Before writing this article, I perused an issue of a magazine dedicated to color and specifically flexo printing. But to my dismay, their flexo was not my flexo. Flexo printing on corrugated is a whole different beast than flexo printing on a web press. All the rage right now seems to be color consistency of the brand among all forms of the product in packaging, on a display, on the web, in print, and with the product itself. The interesting thing is that the degree of color accuracy that is routinely achievable in most forms of printing can be quite challenging for flexo on corrugated. As a graphic designer for (far too?) many years and having come from the advertising agency side of the industry, I found that I had to adjust my way of thinking about what it means to be color-​accurate and consistent. In the offset litho world, achieving a color variance of Delta 2 E is the norm for acceptable color throughout a run and among different press runs. But when it comes to flexo direct to board, we have to deal with many more variables to achieve consistent color than with other printing methods. The theory is that flexo ink is mixed, based on a given formula, to simulate a PMS color for a particular substrate, and it should be good to go. The reality is that even though the ink drawdown was done on the type of liner that will be used in the actual run, there are differences in color among paper mills and batches of board. Though mottled white is a standard board type and the color has gotten much more consistent over the years, there still can be some variation. In comparison to a nice white piece of paper, MTW can be a bit green, which gives a color cast to any ink colors applied. It can really throw off a blue because it cancels out the red in the formula. Kraft board has an even wider variation in color that makes it unsuitable for color-critical work. Other variables that can affect the color are the warp of the board, the hold out of the board, the pressure needed to get a good print, the length of the run, etc. Being out at press-side, it is humbling to see your perfectly matched-to-the-PMS-book ink drawdown actually print out on the corrugated sheet looking completely different. It can be too dark, too light, splotchy, have uneven coverage, etc. So, now what? You gather your ink person and press operators together to brainstorm on what to do to get the color right. Add a little water, maybe some more vehicle, add some base—these are some of the adjustments that can be made to the ink. The pH and dryer temperatures can also be adjusted. Every change needs to be made in small steps and has to be meticulously recorded so it is repeatable for the next run. Plus, the ink can get lighter or darker throughout the run as the board sucks the moisture from the ink, making the base stronger. Then there are the viscosity changes through the run, especially with vacuum transfer, which can change two to three times faster and needs to be checked every 10–15 minutes. Physical changes may come into play as well—maybe back off on the plate pressure or add more pressure to board, adjust the doctor blade to change the ink film thickness, or maybe go with skip feed. Once the color is good, you spot-check it with a photospectrometer to make sure your color stays within the Delta 2 range, making adjustments as needed—and then your shift ends. The next day you get out that same bucket of ink, same batch of board, get the press up and running again, and lo and behold, the color is different! Getting color consistency for a brand is possible but challenging when printing direct to corrugated board. The packaging or display may be the first piece a consumer sees before getting their hands on the actual product, so the color needs to be “right” in their eyes. The designer of the packaging or display needs to work with sales to manage client expectations and anticipate the realities of flexo print on corrugated. Get the production team involved early in the process to identify areas of concern, and adapt the design to the strengths and limitations of manufacturing. If the color of the branding will be affected by the board type, then use that color as an accent, not on a really large area that will be difficult to hold on press. Design to the strength of flexo, not its weaknesses, and know that you can basically get consistent color.

width=150Peggy M. Underwood is graphic design manager at Corrugated Container Corporation in Roanoke, Va. She can be reached at