The Lowdown on Low Migration Inks

Only in packaging is it possible to specify a production ingredient that doesn’t formally exist – and then print with it.

This unicorn among consumables is known as low migration (LM) ink, and it does a very real job of protecting foods and other consumer products against chemical contamination. But nothing about it, from its semantics to its chemistry, is simple or straightforward – a fact for printers and converters to remember as they navigate the thicket of domestic and international regulations that govern how low migration inks are to be classified and used.

The basic conundrum is that there is no standard definition of “low migration ink” among ink manufacturers. “If you find a ‘precise’ definition, I’d love to poke holes in it,” says Russell Szadowski, director of analytical R&D, INX International Ink Co.

Understanding ink migration is important in a variety of markets, including food packaging.

“I wish there was [a definition],” admits Heather Rockow, manager of energy curable business development for Kao Collins Inc., adding that “low migration” is more a marketing term than a scientific one.

It’s not that the ink manufacturers don’t know what they’re compounding. It’s that the regulatory powers-that-be don’t concern themselves with the ink per se.

Directives from the U.S. Food and Drug Administration (FDA) apply only to ink ingredients that, through migration, can become part of the food inside the package. The same is true of European specifications – principally the “Nestlé list” and the so-called Swiss Ordinance – that spell out the migratable materials that may be present in ink or have to be excluded from it. In neither the U.S. nor the European body of rules is approval given to or withheld from the ink itself.

This is why the National Association of Printing Ink Manufacturers (NAPIM) advises packaging converters against thinking that it’s only necessary to use inks billed as “low migration,” “FDA Approved,” or “Nestlé compliant.”

“There is no such thing as an ‘FDA approved ink’ as the FDA does not approve or regulate inks or coatings but only regulates substances that are intentionally or unintentionally added to the food itself,” NAPIM states in An Industry Guide for the use of Printing Ink On Food Packaging 2018.* “If a component of the ink does migrate into the food above recognized threshold levels, it needs to be a substance approved by the FDA as a food additive, or there will be liability issues.”

“Recognized threshold levels” refers to the allowable limit of ink components or other substances in food when migration does occur, measured in parts per billion (ppb). Although thresholds in the U.S. can range to 50 ppb, many consumer product manufacturers default to the lower (10 ppb) European cut-off as a safeguard.

Fifty years ago, says Szadowski, 50 ppb was the limit of threshold detection; concentrations smaller than that couldn’t be measured by systems then available. Today, anything less than 10 ppb is seen as equivalent to zero migration. But that doesn’t mean the regulatory thresholds can’t go lower, because as Szadowski points out, detection methods are getting more sensitive all the time.

Metal, glass and laminate structures act as functional barriers that keep ink away from food, but other types of packaging materials don’t provide this kind of protection. Adding to the difficulty of determining how migration will occur in packages made of non-barrier materials is the fact that the phenomenon is application-specific.

Rockow notes that migration testing protocols depend, for example, on whether “frozen foods at zero degrees or dog food at room temperature” is the packaged good being analyzed.

John Kilbo, OFC regional technical manager for Siegwerk USA, acknowledges that there’s no “sanctioned definition” of UV low migration ink. As a practical one, he suggests identifying low migration inks as those that can do two things: print at “profitable press speeds given normal densities and aesthetics”; and counteract the two chief causes of migration. These are passage of ink components through the packaging material; and ink setoff occurring because of contact between the printed sides and undersides of packaging materials wound in rolls or stacked in sheets.

Food isn’t the only market segment where ink migration can be an issue. Rockow notes that pharmaceuticals also need protection against it, as do medical supplies such as syringes, intravenous fluid bags, and artificial limbs.

Despite the potential for exposure and liability, however, packaging with low migration ink has a largely trouble-free track record in all of these categories. This is partly due to broad observance of the FDA’s Good Manufacturing Practices (GMPs) for the safe manufacturing, packing, and holding of foods and other products. George G. Misko (Keller and Heckman LLP), an attorney who specializes in food and drug matters, says supply chain cooperation in food safety is one reason why “acute toxicity issues” seldom if ever arise in this area of packaging.

Advancements in ink technology are helping the manufacturers to develop products that protect food safety without compromising ink performance. Kilbo says, for example, that the “20% rule” that used to apply to UV low migration inks – “expectations of a 20% weaker product, 20% slower cure speed, and 20% more costs involved versus a non-low migration product” – is being rolled back by fast-curing LED UV systems that make working with these inks much less problematic.

Adherence to GMPs is another driver of progress in low migration inks. Kao Collins insists on getting the latest test data from its raw material suppliers, according to Rockow. The company subjects incoming ink ingredients to its own quality-control scrutiny and tests compounded inks before shipping them, having also examined their interactions with substrates and their drying/curing properties.

Similarly, at INX, which has been making low migration inks for more than 30 years, “we work to mitigate any deficiencies in the printing prior to release to market,” Szadowski says.

These best practices make it possible to qualify inks as “low migration” without affecting their print quality in any way. As Rockow notes, a low migration ink that doesn’t look good isn’t an ink that customers are going to want to buy. “It’s got to be pretty” and as dependable as non-low migration inks in order to be marketable, she says. Kilbo points out that thanks to stronger pigment loadings in UV low migration inks and the greater curing efficiency of LED UV systems, “there is simply no reason left for not making a transition to LM printing if the application demands it.”

Making low migration inks better at what they do comes with a price tag, however. What Kilbo calls “the best molecules” – the ingredients that give LM inks their special properties – tend to be scarcer and more expensive than the raw materials of non-LM inks. To minimize the risk of contamination, LM inks must either be made on dedicated equipment (as Siegwerk does) or purified after formulation.

A variety of markets can benefit from low migration ink. Photo courtesy of Siegwerk.

However, despite all of the care taken on the manufacturing side, there can be no guarantee that migration of ink components – or of other substances – won’t occur if printers and converters aren’t cooperating in preventing it.

This is because when migration takes place, factors other than the ink could be responsible for it: for example, substrates; press and pressroom conditions; and the presence of other consumables such as coatings, adhesives, and non-LM inks (which can permeate roller trains in offset equipment, leaving migratable residue behind).

Szadowski says that in performing LM testing for INX customers, he has discovered traces of plasticizers, fountain solution, and silicone lubrication fluids in their production equipment – all of which can migrate, and all of which will be detectable when they do.

NAPIM’s position in its guide is that “ink or coating manufacturers can only exercise control over their choice of raw materials and manufacturing procedures, so as to minimize the introduction of unapproved ingredients and contaminants. They cannot control the conditions under which the ink is subsequently used, or the substrates on which it is printed.” As Szadowski puts it, “it’s hard for us as ink companies to know what our customers will do with the ink” once it is in their hands.

What they should be doing, according to Kilbo, is building a “working process window” within which they can print LM work in keeping with the requirements of GMP. Printers that don’t adopt GMP routines “are destined to fail at some stage,” he warns.

Ultimately, says NAPIM’s guide, “‘low migration’ is a discipline, not a type of ink.” As a discipline, it’s a holistic responsibility that encompasses, according to Kilbo, printing ink, package design, effective barriers, and processing conditions. “Most printers realize there are no blank checks in this game,” he says.

Rockow also emphasizes that when packages are evaluated for LM compliance, more than just the ink will have to score passing grades. The FDA may wish to examine the entire sequence of producing a package, so printers and converters should be prepared to show relevant test data for all components and manufacturing steps.

In the U.S., says Szadowski, the essential document on migration testing for food packaging is the FDA’s “Guidance for Industry: Preparation of Premarket Submissions for Food Contact Substances (Chemistry Recommendations).” A glance at its highly complex requirements adds urgency to Misko’s advice that printers and converters seek “adequate assurances” from their ink suppliers about the safety and suitability of their LM products.

They also should remember that regulations governing LM inks change continuously, usually in the direction of becoming more stringent. This is why Kilbo advises printers to keep an eye on the strictest standards of compliance even if they are not currently bound by them.

“Eventually,” he says, “that’s where things end up.”

*For more information on An Industry Guide for the use of Printing Ink On Food Packaging 2018, contact George Fuchs, NAPIM’s Director of Regulatory Affairs and Technology, at (770) 209-7291