Ink-Substrate Interactions...

the Good, the Bad, and the Ugly

Broadly speaking, there are two kinds of ink-substrate interactions: desirable and undesirable. Desirable ink-substrate interactions are defined by their outcome: satisfactory ink adhesion; appropriate scuff-, weather-, or moisture-resistance; light-fastness, color-fastness, printability, etc. Undesirable interactions fail on one or more counts. This is true for all forms of printing, but is especially so in package printing, given the vast array of substrates used in packaging.

All of which is to say, somewhat axiomatically, that a product’s end use will—or should—determine the materials and the processes used to produce it, as well as a determination of the post-press finishing and handling it will undergo. Often overlooked, says Russ Barton, director of operations, demo rooms for Heidelberg USA (www.heidelberg.com), is that package printing, per se, is just an early chapter in the production cycle.

“We forget that printing isn’t the biggest part of package production,” Barton says, observing that additional finishing processes such as stamping, embossing, folding, and gluing, etc. also will affect the initial choice of substrate and ink. In other words, “If it looks good on press, it’s only part of the story.”

“Ideally,” says Barton, “your choice of substrate and ink would start with a discussion between the package designer and the end-user, taking into account not only the graphics and the layout, but also a determination of how the box is to be printed, processed, handled, shipped, used, and displayed.” Physical properties such as adhesion and scratch resistance of the final package are determined by a combination of factors, including ink, substrate, and surface treatments, all keyed to end-use requirements.

So the question becomes, how to optimize ink-substrate performance during printing while meeting all customer requirements for the end use of a product. For example, Barton explains, there are food-level inks that have to be edible if they come in contact with the product to prevent toxins from leaching into the food. By the same token, he says, inks and materials used to create a box of fish sticks or the label on a bottle of wine destined for the ice bucket will have different requirements than those used to create a cereal box, based on color-fastness and moisture-resistance.

Think ink

Basic incompatibilities between substrates and inks are often overlooked due to a lack of communication among the designer, printer, and ink supplier. In reality, experts say, ink is often treated as an afterthought.

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