Ink migration is one of those subjects that stays invisible until a retailer asks a question you cannot answer. The short version: substances from printing inks, coatings and adhesives can travel into food through the board, through the gas phase, or by direct contact with the printed surface. None of this means printed packaging is unsafe by default. It means the material set and the print layout have to be chosen for the food, not for the shelf photograph.
What exactly is ink migration? It is the movement of ink components – mineral oil hydrocarbons, photoinitiators, plasticisers, heavy metals from certain pigments – from the printed layer into the packaged product. Three routes matter: set-off where printed sheets stack and ink transfers to the reverse side, penetration through porous board, and vapour-phase transfer where volatiles pass through the pack into the food.
Which packaging is most exposed? Dry foods with large surface contact and long shelf life carry the most risk: cereals, pasta, rice, biscuits, tea, chocolate. Fatty foods absorb migrants more readily than dry ones. Small packs with a high surface-to-product ratio are worse than large ones, and a pack stored warm for months is worse than one sold in weeks.
Is food-grade board enough on its own? No. Board can be made from virgin pulp and still carry migrated ink from the printed outer surface, or from adhesives and coatings applied later. Compliance is a property of the whole pack – substrate, ink system, coating, adhesive, and the way they interact – not of any single certificate. What the material rules cover is set out in the guide to food contact, REACH and RoHS.
Which ink systems reduce the risk? Low-migration offset inks formulated for food packaging, water-based flexo inks, and UV inks with low-migration photoinitiator packages all exist for this purpose. The larger factor is often the layout: keeping heavy ink coverage away from the food-contact side, and avoiding full-bleed printing on the inside of a carton, reduces exposure more reliably than switching ink brands.
What does a functional barrier do? A barrier layer – typically an aluminium-free metallised film, a dispersion coating, or a PE liner – sits between the print and the food and slows migration to a rate the shelf life can tolerate. Barriers are not absolute; they are specified against a migration limit and a duration. A pack designed for a nine-month ambient shelf life needs a different barrier from one sold within six weeks.
How is migration actually tested? Normally by a laboratory using food simulants and conditions that represent the intended use – time and temperature matched to storage. Results are reported per substance against the applicable limit, not as a single pass or fail. Testing is done on the finished pack, because the same inks on a different board can produce different results.
What should I ask a supplier before ordering? Ask which ink system they propose for a food pack, whether they can supply a migration test report on the finished structure, whether they hold declarations of compliance for board, ink and adhesive, and whether the layout keeps print off the food-contact surface. A supplier who answers all four in writing is telling you something useful about their process.
Does a certificate remove the need to think about this? No. A material declaration covers the material as supplied, not the printed pack as manufactured. Ink cure, press conditions, stacking and storage all affect the final result, which is why brands with food ranges test the finished article rather than filing paperwork and moving on.
Where does odour fit into this? Closely related and often confused. Odour problems are usually volatile compounds from ink, glue or board rather than migration, and they show up as a smell when the pack is opened. Tackling one does not automatically fix the other, and the checks differ – the packaging odour FAQ covers that side, while the formulation choices sit in the notes on controlling odour through inks, glues and boards.
If you are developing a food pack and the migration question has come up late, send the structure you have and the intended shelf life. We will tell you what the ink and barrier choices look like at our Wuhan plant and what documentation we can supply with the order. Start on the quote request page.
Chengtop produces folding cartons, corrugated shipping boxes and rigid gift boxes from our plant in Wuhan. For food-contact projects we quote the ink system and barrier as separate line items so the cost of compliance is visible rather than buried. Message us with the product and shelf life and we will respond with options.
