Blister-Pack Printing: Key Factors Affecting Print Performance

Blister-pack printing is a compact process that concentrates a lot of variables into a small print area. When it works well, it is invisible; when it does not, it can hold up a batch. This article summarises the factors that most often affect print performance on blister-pack aluminium foil, based on the applications Axion Group sees across the pharmaceutical manufacturers we work with.

The foil–ink interface

The interface between the aluminium foil and the printing ink is where most performance issues begin. Foils vary by:

• Lacquer composition and coverage — the print side of most pharma foils is lacquered, and small differences in coverage change wetting behaviour.
• Surface energy — a foil batch with lower surface energy than expected can produce dewetting, mottling, or poor adhesion.
• Micro-roughness — even within one supplier's grade, roughness can vary by lot; this affects the amount of ink transferred and the appearance of the printed image.
• Storage history — foil stored in high-humidity or contaminated environments can carry surface contamination that interferes with print.

The practical takeaway: treat every new foil lot as a new variable, especially when a print performance issue appears.

Press setup and impression pressure

Blister-pack printing is typically performed on rotogravure or, on some lines, flexographic presses. Setup variables that most commonly affect print quality:

• Impression pressure — under-pressure produces broken-up marks; over-pressure produces smearing and reduced legibility.
• Anilox / cylinder condition — worn engraving reduces ink transfer; contaminated engraving reduces coverage evenly across the image.
• Plate or cylinder alignment — misalignment produces registration issues that can be mistaken for ink problems.
• Web tension — over-tension or slippage changes the effective press geometry and can shift ink transfer.

When investigating a print defect, a systematic pass through the press setup is a reasonable first step, even where the ink is the newest variable.

Drying and cure conditions

Blister-pack inks are typically dried through a combination of solvent evaporation and, in some cases, additional cure. Drying variables to check:

• Oven / dryer temperature — a small drift in dryer temperature can move an ink from adequately cured to under-cured, particularly at higher line speeds.
• Web residence time — if line speed is increased without adjusting dryer output, the effective drying time falls.
• Ambient humidity — high-humidity environments slow solvent evaporation of some ink chemistries.
• Downstream process temperature — subsequent forming and sealing steps expose the printed image to additional heat, which can affect apparent cure state.

An ink that appears to work on a bench trial but fails in production is often being run at a shorter effective drying time than the bench trial allowed for.

Ink handling and storage

Blister-pack printing inks are sensitive to how they are handled between delivery and use. Common handling issues:

• Solvent evaporation during storage — partially used containers left open change the ink's viscosity and can shift performance.
• Contamination from cleaning solvents — press-side cleaning solvents can carry across into the ink if handling procedures are not tight.
• Age since manufacture — many inks have a documented shelf life; using ink close to or beyond that window can produce inconsistent behaviour.
• Storage temperature — cold storage or high-temperature exposure can affect solvent balance and pigment dispersion.

A short standard operating procedure at press-side — closed lids, defined shelf-life labelling, controlled decanting — resolves most of these issues.

When to involve your ink supplier

Escalate to your ink supplier when:

• A defect appears that a systematic press and substrate review does not resolve
• A foil supplier or grade changes and the previous ink no longer performs
• A new pack format, orientation, or downstream process is being introduced
• A verification failure appears that is not attributable to the verification system itself
• The team wants to consolidate multiple ink references onto fewer SKUs

Involving the supplier early — with the substrate lot, press settings, line data, and defect samples — shortens the resolution loop. A supplier that expects to be involved only after the internal investigation is exhausted is not being used effectively.

If your team is investigating a blister-pack print performance issue or planning a change of ink, foil, or line, Axion Group can help work through the variables. Product suitability remains subject to application testing under the customer's actual production conditions.