Low Migration Is Not Less Migration

Executive summary

UV-cured inks and coatings are attractive for food packaging — no solvent, instant cure, high resistance — but every UV product contains photoinitiators and monomers, and any of them that survive cure unreacted can migrate through the pack into the food. This paper explains the migration routes, the difference between “less migration” and genuine “low migration” chemistry, the regulatory framework in Europe and Switzerland, and how Uniform Industries’ UniCure FP inks and low-migration coatings are designed and — equally important — how they must be used to achieve compliant packaging.

1. How a cured ink can still migrate

Three routes exist. Permeation through the substrate: relevant on plastics and thin paper, negligible on foil. Set-off: the printed outer surface touches the inner, food-contact surface of the next sheet or the next lap of the reel, transferring residues directly — the dominant route for paper and board, and one that a barrier substrate does not stop. Gas-phase transfer of volatile components through headspace. What migrates is whatever is small, mobile and unreacted: residual monomers, photoinitiator molecules that were never activated, and photoinitiator fragments produced during cure — benzophenone, ITX and their photolysis products being the historical offenders.

Figure 1 – Set-off transfers residues to the food-contact surface of the next sheet or reel lap (schematic).

2. Two philosophies

A less-migration ink keeps conventional chemistry and chooses heavier molecules: high-molecular-weight photoinitiators migrate more slowly because they are big. They still migrate. A low-migration ink uses photoinitiators that are themselves polymeric or carry acrylate groups, so that during cure they react into the polymer network and become part of the film. Combined with oligomers and monomers of high molecular weight and low volatility, and with pigments that do not carry soluble fractions, this is chemistry that leaves little that can move. UniCure FP is built on this second principle: cross-linkable polymeric photoinitiators from Groups 1A and 1B of the EuPIA suitability list, no low-molecular-weight acrylates, no Fanal pigments, no mineral oils.

3. The rules

Regulation (EC) 1935/2004 (framework): materials must not transfer constituents to food in quantities that endanger health or change the food. Article 17 requires traceability.

Regulation (EU) 10/2011: specific migration limits for plastics; used by analogy for the plastic layers of laminates.

Swiss Ordinance SR 817.023.21, Annex 10: the only statutory positive list for packaging-ink substances; Part A (evaluated, with limits) is the reference, and since the 2024 revision — transition ended 31 January 2026 — non-listed substances are permitted only if free of CMR properties and shown to migrate below 10 µg/kg.

German Printing Ink Ordinance (GIO / Druckfarbenverordnung): positive list on the Swiss model, transition ended 1 January 2026.

EuPIA GMP guideline and, from March 2026, the EuPIA Charter: the industry’s manufacturing and raw-material selection standard.

None of these certifies an ink. They set the frame within which the finished pack must be shown to comply.

Figure 2 – Specific migration against UV dose: cure is the largest lever, LM chemistry lowers the floor (illustrative).

4. Why the printer holds most of the levers

Migration is proportional to the amount of ink and inversely related to cure. The converter controls both.

Cure is the single largest lever. An under-cured film leaves monomers and initiators free. Establish the speed–dose window that gives full cure on the darkest colour, run inside it with a safety margin, and log lamp hours and radiometer readings.

Ink load: print standard densities and keep total deposit at or below 2 g/m²; more ink is more potential migrant.

Set-off control: cool the web, control stack pressure and reel tension; set-off defeats a barrier substrate.

Hygiene: only food-packaging auxiliaries (reducers, cleaners, varnishes, adhesives) on the press.

Substrate: porous or recycled stock brings its own migrants and absorbs uncured ink.

Traceability: batch numbers, printing conditions and recipients recorded for every job.

5. Proving compliance

The printer or packer commissions migration testing of the finished pack by an accredited laboratory: overall and specific migration to the simulant appropriate to the food (Regulation (EU) 10/2011 protocols), a screening for photoinitiators and acrylates by GC-MS / LC-MS, and organoleptic testing (DIN 10955). EuPIA’s guidance expects an iterative approach — test, correct, re-test — and a documented safety margin across the press-speed range. Uniform Industries supplies a statement of composition under confidentiality agreement listing every potential migrant, which is the starting point for the laboratory’s target list.

6. UniCure FP and the low-migration coatings

UniCure FP flexo inks (Pantone base range, process set, whites) are matched by low-migration overprint varnishes — UniCure 2010RC for sheet-fed and UniCure LMC 83RC / LMM 72RC for narrow web — built on the same polymeric-initiator technology, so that the full structure of ink and varnish can be qualified together. Independent migration measurements on standard label constructions have shown results below the industry guideline values at the recommended cure and ink load.

Key takeaways

Set-off, not permeation, is the main migration route on paper and board.

Low migration means initiators that react into the film, not just heavier ones.

Cure, ink load, set-off and hygiene are the printer’s controls — and the biggest ones.

Compliance is demonstrated on the finished pack by testing; the ink supplier provides the chemistry and the composition data.

References: Regulation (EC) 1935/2004; Regulation (EU) 10/2011; SR 817.023.21 Annex 10; EuPIA GMP Printing Inks for Food Contact Materials; EuPIA Charter 2026; DIN 10955.