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Back in the 1990s when I was an art director/production manager, the nonprofit educational foundation for which I worked bought roll labels with a logo, a little bit of type, and room to write participants’ names in magic marker.

If you looked really closely, you could see a slight difference in ink density between the edges of letters or art and the center of the text or image. These were very simple label imprints on matte label stock, so there were no issues with precise halftone details or with tight register of colors. That said, this was a commercial printing technique very different from the offset lithography used for all of the other jobs at my organization. (BTW, we didn’t have digital custom printing yet.) This printing technology was called flexography.

Flexography uses rubber plates wrapped around cylinders (i.e., on a rotary press) to print on any number of substrates. Image areas (type and art) are raised on the rubber plates. That is, this is a relief process unlike offset which uses the immiscibility of oil and water (oil and water repel one another) to allow both image and non image areas of an offset lithographic plate to be on the same flat surface (i.e., planographic rather than relief).

Flexography, then, is akin to letterpress (albeit on a rotary press rather than a flatbed press and using rubber plates rather than metal plates).

What Are the Specific Components of Flexographic Printing?

As with offset lithography, the flexo ink resides in a well on each inking unit of a flexo press. The ink is brought up onto an anilox roller which is covered with wells (like a gravure press cylinder). A doctor blade wipes off any excess ink. This anilox roller then deposits the required amount of ink onto the rubber plate (which is taped to a sleeve on the plate roller). From the rubber plate the ink is applied to the substrate. An impression roller keeps the printing plate tightly pressed against the substrate to maintain precise transfer of the ink from the plate to the substrate.

(Remember that this is in contrast to offset lithography, in which the image is printed on the press blanket first and is then transferred from the blanket to the substrate.)

Each color has its own inking unit. And further along, after the inking units on the press, there are finishing units attached as needed for a seamless custom printing and finishing workflow.

Why Would Someone Choose Flexography?

Multiple Printing Substrates

On an offset press, you can’t print on all possible substrates. In fact, printing on a non-porous substrate would be especially problematic. That said, on a flexographic press, you can use a water-based, quick-drying ink (dried with heat), and this allows you to print on plastic sheeting (to wrap bags of bread for the grocery store), wallpaper, paper cups, foil, cellophane, fabric, plastics, metallic labels, envelopes, milk and cereal boxes, shopping bags, corrugated board, and wrapping paper, to name a few substrates. A lot of companies even use flexography for newspaper printing.

A Variety of Appropriate Inks

On a flexographic press, you can use water-based inks as noted above, but you can also use solvent-based inks (as you do in offset lithography). Plus you can use UV inks (cured with UV light rather than heat). So you have more ink options than you do with offset lithography.

In addition, with flexography, you may have multiple ink stations (more than the four in offset lithography for cyan, magenta, yellow, and black), so you can more easily add PMS colors to the job. (Granted, six- and eight-unit offset presses can do the same thing.)

And flexo inks are not as viscous as offset commercial printing inks. Therefore they will dry more quickly.

Also, in offset lithographic commercial printing, the process colors are transparent. You create different colors by overlaying various halftone percentages of each of the four process colors. In flexography, however, the inks are more opaque. In fact, you can even approach the thickness of ink achievable with custom screen printing when you’re using a flexographic press.

So overall, ink flexibility is a major plus of flexography.

Long-Lasting Printing Plates

Even though they are made out of rubber (a photopolymer compound, actually, that can be imaged with a laser and then processed with a solvent to remove excess rubber from the non-image areas), flexographic plates can last a long time, up to several million impressions, which is a lot longer than the life of many metal offset printing plates. This will save you money in platemaking.

The Speed of Flexography

Once up to speed, flexo printing can be faster than offset lithography.

Inline Finishing Options

For the most part, if you were producing a job via offset lithography, you would complete the printing process and then bring the press sheets into the finishing department for further work. However, with flexography, you can set up finishing operations such as laminating, slitting, trimming, and die cutting inline with the custom printing. This will make the overall manufacturing process take less time, which will translate into dollars saved.

Detail, Precision, and Resolution

Back when I was an art director in the 1990s, flexography was not the most precise commercial printing technology. Since the plates were rubber, and since this was essentially a “stamping” operation, the flexo plates moved around slightly. This meant registering one color to another precisely was not always possible, and it also meant that dot gain would be higher than with offset lithography (halftone dots would spread and print darker, or actually larger, than intended).

However, based on all my reading for this article, it seems that precision within the realm of flexography has improved considerably in the last thirty or so years. Presumably this allows for finer halftone screens, tighter register, and less dot gain than before.

In addition, there has been increasing automation within the printing industry (including flexography). For instance, if you look at the bottom of a cardboard orange juice container printed via flexography, you will see printed targets that allow for closed-loop electric-eye monitoring of (as well as computer control over) color accuracy and tight register on press.

The Takeaway

That said, if you are considering flexography for one of your commercial printing jobs, I’d encourage you to review printed samples first to make sure that the resolution of images, register of color plates, and evenness of ink application are suitable for the product you are printing. If they are, flexography can be a highly economical option.