Achieving Consistent Braille Legibility Across Packaging Substrates

Introduction: The challenge of maintaining consistency across diverse substrates

Tactile legibility is the primary performance measure for compliant pharmaceutical Braille. Yet achieving consistent results across folding cartons, laminated labels, polymer containers and foil substrates can be difficult. Substrate stiffness, thickness, coating, fibre density and finish all influence tactile clarity, height retention and durability of Braille dots. Even when artwork is correctly set to the Marburg Medium specification using PharmaBraille fonts, variations in material and process can compromise readability during production and downstream handling.

Key development: material performance and tactile sensitivity

Research and industry practice show Braille readers are sensitive to small changes in dot elevation and uniformity. Materials with inconsistent grain or heavy coatings may cause surface fracture (“burst-through”) or dot collapse, while overly stiff substrates can limit achievable dot height; conversely, very soft materials are prone to deformation during distribution. Consistent legibility therefore depends on a balanced system: appropriate substrate selection, correctly specified artwork and well-calibrated embossing or print-build processes.

Technical/regulatory impact: core requirements in ISO 17351

• Dot height (embossed materials): target 0.20 mm; ≤ 5 % of measurements may be < 0.12 mm; ≤ 1 % may be < 0.10 mm. Measurements taken along the Braille line using calibrated spring-loaded micrometers.
• Dot height (other methods, e.g., screen-printed labels): target 0.20 mm; ≤ 5 % of measurements may be < 0.16 mm.
• Spacing: adopt the Marburg Medium spacing convention (dot, letter, word and line spacing with ± 0.1 mm tolerances).
• Demonstrating compliance: verify dot height per Annex A, or where height cannot be verified, carry out legibility testing with qualified Braille readers against an agreed protocol.
• Printed text integrity: Braille must not compromise the legibility of ink text or graphics; visible burst-through should be avoided.

Actionable implications: a practical checklist

1) Material selection

• Pre-qualify board grades, label stocks and coatings specifically for Braille embossing or print-build. Avoid excessively hard, highly varnished or heavily laminated finishes that restrict dot formation.
• Assess compressibility, rebound and fibre structure. Confirm that dot elevation is maintained after folding, gluing and transport simulation.
• For labels/foils, factor in ink and adhesive build-up that can blunt or distort dot geometry.

2) Artwork and spacing

• Set Braille to Marburg Medium dimensions in artwork. With PharmaBraille fonts, use 10 mm font size and 10 mm line spacing (100 %) to achieve the correct dot, letter and word spacing.
• Keep Braille on a separate artwork layer. Reserve a clear “Braille register point” and maintain adequate clearance from creases, cuts and critical print.
• Confirm the correct national Braille character set for each market; avoid unnecessary capital indicators and trademark symbols unless legally required.

3) Embossing and print-build calibration

• Validate male/female die alignment, pressure uniformity and makeready across the sheet or web. Re-validate after tooling repair or changeover.
• For single-pass cut/crease + Braille, verify that cutting pressure does not affect dot height. For two-pass flows, lock down register and handling to prevent dot damage.
• Where using screen/inkjet build, confirm cured dot height, profile and adhesion; ensure dots remain transparent to preserve underlying print legibility.

4) Verification and legibility testing

• Measure dot height at three or more points per Braille line using a calibrated micrometer; record results to two decimal places.
• Define acceptance criteria aligned with ISO 17351 tolerances. Where physical measurement is impractical, conduct reader-based legibility testing using a documented protocol.
• Retain golden samples by substrate and keep batch-level retains for traceability.

5) In-process and incoming quality control

• Perform random checks across multiple press stations; recheck after any tooling or setup change.
• Uniquely identify Braille tooling and keep calibration and maintenance records.
• At goods-in, verify translation accuracy, placement, printed text integrity and tactile uniformity before release to pack-line.

References

• ISO 17351:2013 — Packaging — Braille on packaging for medicinal products
• Marburg Medium spacing convention (blista) — Braille dimensions
• MHRA — Labelling guidance (Braille requirements)
• PharmaBraille — Pharmaceutical Braille fonts & resources