A barcode that looks perfect on the artwork proof can still fail on the packaging line. The design file is vector-sharp; the real pack is ink on foil or board, printed at line speed, sometimes under varnish, often on a curved or reflective surface. Most barcode failures in pharma aren't data problems — they're printing problems. The code carries the right information, but the scanner can't read it reliably, or a verifier grades it below the level GS1 expects.
This guide covers the printing side: which technology to use for which pack, how big the code needs to be, what print-quality grades mean, and the mistakes that make a compliant barcode unreadable. It picks up where generating the code leaves off — if you still need a GS1 Company Prefix and your first GTIN, start with how to generate a GS1 barcode in India.
Static vs Variable: Two Different Print Jobs
Every pharma barcode has a static part and a variable part, and they are usually printed in different places by different machines.
- Static data — the GTIN and fixed product text — never changes for a SKU. A plain EAN-13 carrying only the GTIN can be printed with the carton artwork itself, by offset or flexo, at the printing press.
- Variable data — batch number, manufacturing date, expiry and any unit serial — changes per batch or per pack. Any code that contains it has to be printed on the packaging line, at the moment of packing, by an on-line coder.
A Schedule H2 code carries batch and dates, so it is always a variable print job. That makes the choice of on-line coder the single biggest factor in whether your codes read well.
Choosing a Print Technology
| Technology | Best suited for | Strengths | Watch out for |
|---|---|---|---|
| Thermal inkjet (TIJ) | Cartons, labels, porous board | High resolution, crisp 2D codes, clean cartridge system, common on Indian carton lines | Ink adhesion on foil and coated surfaces; drying time before the next station |
| Continuous inkjet (CIJ) | Bottles, caps, high-speed lines, non-porous surfaces | Very fast, prints on curved and difficult surfaces | Dot-based output is lower resolution — small 2D codes can lose definition |
| Laser marking | Coated cartons, labels with a laser-reactive layer | Permanent, no ink or consumables, very hard to tamper with | Needs the right substrate or coating to give enough contrast |
| Thermal transfer (TTO) | Flexible films, foil lidding, labels | Sharp, high-contrast print on films and foils | Ribbon consumption; needs a flat backing at the print point |
| UV inkjet | Foil blisters, non-porous materials | Ink cures instantly, adheres to difficult surfaces | Higher equipment cost; curing setup on the line |
There's no single right answer. A plant often runs TIJ on cartons, thermal transfer or UV on foil, and a label printer for shippers. What matters is matching each coder to its substrate and confirming the output grades well at full line speed, not just during a slow test run.
Getting the Size Right
Barcode size is controlled by the X-dimension — the width of the narrowest bar in a linear code, or of a single square module in a 2D code. GS1 publishes symbol specification tables that set a minimum, target and maximum X-dimension for each symbol and application.
- GS1 DataMatrix on healthcare items: GS1's healthcare tables set the minimum X-dimension for ink-printed DataMatrix at 0.254 mm. Going smaller to squeeze a code onto a strip is the most common reason primary-pack codes fail.
- EAN-13 for retail point of sale: the nominal (100%) size has a module of 0.330 mm, and GS1 allows magnification from 80% to 200%. Truncating the bar height to save space reduces scan reliability and should be avoided.
- GS1-128 on shippers: logistics labels are scanned from a distance, so they use a larger X-dimension than item-level codes.
Just as important is the quiet zone — the clear margin around the code. A GS1 DataMatrix needs at least one module of clear space on every side; a GS1-128 needs ten times the X-dimension at each end; an EAN-13 needs 11 modules on the left and 7 on the right. Text, borders or graphics that intrude into the quiet zone are a frequent, avoidable cause of scan failures.
What Print-Quality Grades Actually Measure
A scanner tells you whether a code can be read. A verifier tells you how well it was printed, by grading it against an ISO standard. ISO/IEC 15415 (2D) and ISO/IEC 15416 (linear) both grade on a 4.0 to 0 scale, also expressed as A to F. The overall grade is the lowest of several individual parameters, including:
- Symbol contrast — the difference between the darkest and lightest areas. Low contrast is the classic problem on foil and coloured board.
- Modulation and reflectance margin — how consistently dark modules look dark and light modules look light.
- Axial and grid non-uniformity — whether the code has been stretched or skewed, often by product movement during printing.
- Fixed pattern damage — damage to the finder and timing patterns that a reader uses to locate the code.
- Unused error correction — how much of the code's built-in redundancy is left after print defects are accounted for.
The overall grade is only as good as the weakest parameter. A code with excellent contrast but a damaged finder pattern still fails.
The Most Common Reasons Pharma Barcodes Fail
- Glare on foil. Reflective aluminium washes out contrast. Print a white ink base under the code, or use a coder and ink designed for foil.
- Low contrast on coloured cartons. Dark codes need a light background. Red is effectively invisible to many red-light scanners.
- Smudging on varnish or UV coating. Leave the code panel unvarnished, or use an ink matched to the coating.
- Stretched codes from line speed. If the encoder and conveyor are out of sync, modules print elongated. Check grading at full production speed.
- Wrong data syntax. A perfectly printed code still fails if the application identifiers are wrong: expiry must be AI (17) in YYMMDD format, the GTIN must be 14 digits with a valid check digit, and variable-length fields need the correct separator.
- Printhead wear. A worn or partly blocked nozzle produces a white line through every code. Without 100% in-line inspection, a whole batch can be coded this way.
QR Code or GS1 DataMatrix?
The Schedule H2 rule accepts either a bar code or a QR code and doesn't name a symbology. GS1 DataMatrix is the long-standing healthcare choice and is generally more compact for the same data. QR codes are what patients' phone cameras open by default, which matters for a code that's supposed to let a patient check a medicine. GS1 Digital Link, which encodes GS1 identifiers inside a web address, lets one QR code serve both purposes — it carries GS1-structured data for the supply chain and opens a verification page on a phone. It's also the direction GS1's Sunrise 2027 transition to 2D barcodes is heading.
Building Verification Into the Line
- 100% in-line camera inspection that reads and grades every code and diverts failures to a reject bin.
- Periodic off-line verification with a calibrated ISO verifier, on a sample from each batch and at every line or substrate change.
- Data checks before print, so a code with the wrong date format or a bad check digit is stopped before it reaches the printhead.
- Records of grading results kept with the batch record, ready for an inspection.
Where Ratifye Fits
Ratifye validates every GS1 application identifier at code generation, so malformed data is rejected before anything is printed. It sends print-ready codes to the TIJ, CIJ, laser or thermal-transfer coders you already have — no new hardware — and each code can carry a cryptographic signature, so the same code that passes verification also proves the pack is genuine when a pharmacist or patient scans it. Verification at the counter takes under 80 milliseconds.
Codes passing on paper but failing on the line?
Ratifye's team can review your coding setup, from data syntax to print grade, and help you get codes that read first time — on the coders you already own. Start with 500 free authentications.
Talk to our teamSources: GS1 General Specifications, including the symbol specification tables for healthcare and retail point of sale; ISO/IEC 15415 and ISO/IEC 15416 print-quality test specifications; CDSCO notification G.S.R. 823(E) and CDSCO FAQs on Bar Code / QR Code implementation for Schedule H2 brands; GS1 Digital Link standard. Figures are drawn from the published standards at time of writing; consult the current GS1 General Specifications and your equipment supplier for line-specific settings.
