Custom Printing: Inconsistent Color in Package Printing

My fiancee and I were in the grocery store a few days ago, and I noticed two packages of brown Jasmine rice. The packages had the same art, typeface, design, etc., but the colors were different. It was only a slightprinted variation. Perhaps no one else would have seen it. But I did, and I pointed it out to my fiancee.

I explained to her that printing on a plastic bag required a different technology from offset lithography. In my experience and study I have always seen flexography used to print on plastic sheeting for bags of bread and rolls, as well as many other product packages in the grocery store, such as milk cartons and frozen food packages.

Flexography uses fast drying inks that work well on non-porous substrates (such as plastic sheeting). It is my understanding that flexography also avoids the high pressure of the offset lithographic rollers, which can disturb the dimensional stability of plastic sheeting (even when the plastic is fed from a roll and kept at high tension to maintain its “flatness” during printing).

In contrast with offset lithography (a planographic process in which the image- and non-image areas of the plate are on the same level), flexography is a relief printing process. The image areas on the rubber printing plates are raised. The raised areas are inked as the rollers turn and then deposit the ink on the substrate using less pressure than offset lithography rollers.

Problems with Flexography

In my experience with flexography (mainly in printing labels), the registration of colors is not quite as precise or consistent as in offset lithography. It’s great for non-porous substrates. It’s cheap, efficient, good for long runs of labels and packaging, but in my experience the color work has not been quite as accurate as I would like. (I just read online that part of the problem is the slight movement of various printing press components during the process.)

When I think back to the flexo-printed bags of Jasmine rice, the first thing I could say is that the technology in use was most probably flexography (due to the plastic substrate). The second thing I could say with confidence is that when colors are out of register (i.e., when the commercial printing plates shift and therefore do not deposit their ink precisely), one of the results is that color shifts can occur. I’ve seen this in offset lithography as well.

Moreover, color shifts I’ve seen often occur in neutral colors. (An off-white might take on a pinkish cast, for example.) On the bags of rice, the color in the two brown backgrounds (neutral ink mixtures presumably containing heavy coverage of all four process colors) showed the most difference from one package to the other. The green grass was slightly off as well.

Why This Is a Problem

I thought about why this was a problem from a design, marketing, and custom printing perspective. Here are a few thoughts:

1. 1. Certain colors, called memory colors, absolutely have to be accurate. For instance, the blue of the afternoon sky cannot be purple, but it can be a lighter or darker blue. Grass has to be within a tight range of green hues, or it just looks wrong. Flesh tones that are too yellow appear jaundiced. We expect certain colors to be consistent. Our eyes (and brains) do not tolerate as much variation in these memory colors as in other colors. On the rice packages, the green grass was “off.”

1. 1. When I saw the color shift in these two packages, they were side by side. The human brain cannot usually remember color for very long, but it can definitely see color shifts when two samples are side by side.

1. 1. From a marketing point of view, color shifts can be a problem. Just as one expects corporate logo colors to be consistent, one expects package coloration to be consistent. Subliminally, in the mind of the consumer, color accuracy can support or diminish the perceived quality of other elements of the brand (for example the taste of the rice). We expect a brand image to always look the same, just as we expect a Chipotle burrito to always taste the same. Even design and printing differences can “dilute” the brand.

1. This is less true now than in the 1990s (when I was an art director/production manager), but there will always be a slight variation in color from press run to press run. If the two rice bags had been printed by two separate printers on two separate dates, there would be some difference in color. Again, it would be more obvious if two printed samples were put side by side. In addition, the color shift would be more pronounced if two different commercial printing technologies had been used (say flexography and digital custom printing) or if the printing substrates had been different.

What You Can Do in Your Own Work

Here are some thoughts:

1. 1. If you are using flat colors for backgrounds, particularly if they are neutrals (not primary colors like red, yellow, and blue, but, as in the case of my rice packages, such mixtures of multiple colors as tan or brown), consider adding a PMS match color. These are mixed, not created from overlaid halftone screens of cyan, magenta, yellow, and black. PMS colors are always consistent. In contrast, if your CMYK process colors are out of register, you may see color shifts. But this won’t happen with PMS colors. That’s why designers specify PMS colors for corporate logos.

1. 1. Based on my own experience, it’s often helpful to avoid colors composed of equal amounts (particularly heavy coverage) of three or four process inks. If these colors are out of register, this can cause a color shift.

1. 1. I have also experienced color shifts when working with the less expensive online printers that often gang up print jobs to keep their prices low. A client of mine had an account with one of these commercial printing vendors, so I had to use its services for a job I designed. To be safe, what I did was design my client’s job with this potential limitation in mind. I chose colors and photos that would work well on a design level even with a certain amount of color variation. You may want to do the same thing.

1. 1. Be mindful of the potential limitation of each commercial printing technology you use. For instance, reversing type out of a heavy solid (composed of all process colors) on a digital press might be problematic. Or, at the very least, you might want to choose a typeface with thicker serifs and strokes in the letterforms (to avoid the serifs’ filling in if the ink flow is excessive). If you’re printing a job via flexography, make allowances in your design for any potential misregistration problems, since these can occur in this technology.

1. 1. When in doubt, ask your printer for samples produced via the commercial printing technology you plan to use.

1. 1. For a critical job, consider attending a press inspection. These are rare these days. I think the last press inspection I attended was in the late1990s. Color consistency is much better these days than in the past. But for food, automotive, and fashion imagery, a press inspection might be worth your time. In this case you will see successive press sheets throughout the press run under 5000 Kelvin lighting (blue-white light, which approximates sunlight). You will see any color casts right away.

1. If you plan to match colors across different commercial printing technologies (offset, flexography, digital printing) and/or different custom printing substrates, make sure your printer can rise to the challenge. Again, it’s always prudent to request printed samples produced via all technologies you will employ (ideally using the same file).

This entry was posted on Wednesday, December 2nd, 2020 at 11:52 pm and is filed under Packaging. You can follow any responses to this entry through the RSS 2.0 feed. Both comments and pings are currently closed.