The ink and the adhesive decide it

Packaging specifications describe substrates in detail and inks and adhesives in a line. In recycling terms the proportions are close to reversed: the substrate is usually fine and the decoration is usually the problem.

Where it goes wrong

De-inking. Some inks release cleanly in a paper mill's pulping stage. Others disperse into fine particles that stay in the fibre and grey the output. A mill receiving too much of the second kind downgrades the whole batch, and mills know which brands send it.

Wash-off. A PET bottle is recycled by grinding and washing at around 80°C with caustic. A label adhesive that survives that stays on the flake. A common hot-melt will not release, so the label travels all the way through and lands in the product as a contaminant.

Metallised layers. A metallised film that looks like a single polymer is not one. A few microns of aluminium is enough for a sorter to call it metal and for a reprocessor to reject it.

The good news

These are the cheapest things in the pack to change. An adhesive swap needs no new tooling, no substrate qualification and usually no artwork change. It is often a fortnight of work against a two-year project for a substrate change, and it can move a pack from unrecyclable to recyclable on its own.

What to ask your converter

Ask for the wash-off test result for your specific label-adhesive-substrate combination, not the adhesive datasheet. The datasheet describes the adhesive. You are shipping a combination, and combinations behave differently from their parts — which is most of what we get paid to find out.