Why Production Trials Matter When Changing Printing Ink

Changing a printing or coding ink on a pharmaceutical production line is not a simple substitution. Even where the new ink is nominally equivalent to the current one, small differences in solvent balance, viscosity, resin system, or additive package can affect print quality, adhesion, drying, and downstream compatibility. A production trial is how those differences are surfaced before they cause a batch problem.

This article explains what a production trial actually tests, the failure modes it detects, and how a pharmaceutical manufacturer can build a supplier evaluation process that is proportionate and practical.

What a production trial actually tests

A production trial verifies that a candidate ink performs correctly under the customer's actual conditions. Bench and lab tests confirm chemistry-level properties; a production trial confirms:

• Adhesion on the specific substrate and lot in use that week
• Drying at the actual line speed and ambient humidity
• Legibility as read by the customer's own verification cameras
• Compatibility with all downstream processes the printed pack encounters
• Reliability across a representative production run, not just a single sample

Bench data alone can suggest an ink is suitable. Only a trial confirms it.

Common failure modes

Failure modes routinely surfaced by production trials include:

• Substrate drift — a substrate whose supplier or lot has quietly changed, revealed by the new ink not performing as it did on samples.
• Line-condition sensitivity — an ink whose adhesion is fine at 22 °C and 50 % RH but degrades at 30 °C and 65 % RH.
• Downstream process interactions — an ink that survives handling but fails after autoclaving, sealing, or a warm-water rinse.
• Verification system mismatch — a code that is human-readable but fails automated verification because of low contrast, halo, or edge bleed.
• Nozzle or plate incompatibility — for coding inks, a chemistry that runs cleanly for the first hour and then begins to clog.

Each of these can produce a batch problem in regular production. Each is detectable in a short, well-designed trial.

Recommended trial parameters

A proportionate trial protocol we suggest with customers includes:

1. Duration — long enough to run at least one full line changeover, one shift change, and one substrate lot change if possible. A one-hour print is not a trial.
2. Sampling — printed samples pulled at defined intervals (start, mid-run, end-of-run) and retained for retest.
3. Test matrix — abrasion, solvent rub, and any relevant environmental exposure. Ideally at initial cure and after 24 hours.
4. Verification — samples read by the customer's own verification cameras or scanners under the customer's own settings.
5. Documentation — a short trial record capturing substrate lot, line conditions, ink lot, cartridge lot, and any deviations. This becomes the evidence base for the change-control decision.

Trials that omit one of these steps often fail to catch the problem they were designed to prevent.

Documentation

The trial record is a valuable artefact beyond the immediate decision. It supports future audits, provides the reference case for troubleshooting after regular supply begins, and is the foundation for any subsequent variation of the ink or substrate. Even a one-page trial record is more useful than an approval decision with no supporting notes.

Axion Group shares trial protocol templates on request. A supplier who resists documenting a trial is a supplier worth reconsidering.

Building a supplier evaluation process

Pharmaceutical manufacturers benefit from a standing supplier evaluation process, so that trials are consistent regardless of which ink or which supplier is being evaluated. A practical evaluation process includes:

• A short technical questionnaire completed by the supplier
• Documentation review by the customer's quality function
• A defined trial protocol appropriate to the ink and substrate
• A formal change-control decision informed by the trial record
• Post-implementation review after the first three production runs

A supplier who cannot support that process is not necessarily unfit; they may simply lack the internal capability to serve pharmaceutical customers well. Axion Group works within customer evaluation processes and can support the documentation the trial requires.

If you are planning an ink change on a pharmaceutical line and want a trial protocol appropriate to your application, get in touch and we will walk through it with you.