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100Module 8 of 15

Metals & Glass

Aluminum/steel formats, coatings, lacquers, decoration. Glass decoration, closures, and compatibility with hot-fill or carbonated products.

7 minutes
materials
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Lesson Video
Metals & Glass
Module Content

1) Executive Summary — Most important insights

  1. Metals & glass are inherently barrier-excellent (OTR/MVTR ~0 through the wall); performance hinges on seams, liners, coatings, and closures—not the substrate.
  2. Food-contact compliance is region-specific (US 21 CFR 175.300/105/ 177.1210; 113/114; EU 1935/2004, 2023/2006, 2018/213 BPA; UK retains EU approach).
  3. BPA risk bar keeps moving (EFSA 2023 → lower TDI). Default to BPA-NI coating systems and obtain migration data.
  4. Closures drive fitness-for-purpose: specify finish/closure systems to ISO/EN/CETIE early (crowns, BVS/ROPP, lugs) with torque/pressure targets.
  5. Glass hot-end/cold-end coatings are essential for handling & label adhesion; design for thermal shock (ASTM C149) and internal pressure (ISO 7458) as applicable.
  6. Steel grades/specs (EN 10202) and aluminum alloys (3004/3104 body; 5182 ends) matter for forming and end performance.
  7. Recyclability labelling rules (How2Recycle/OPRL) can change; sleeves on glass must be perforated to protect sortation.
Priority actions for designers
  • Specify BPA-NI coatings/lacquers and document migration under intended conditions of use.
  • Lock finish–closure standards early (ISO/EN/CETIE) and embed QA for torque, vacuum/pressure, leakage, seam teardown.
  • For hot-fill/pasteurization, require ASTM C149 thermal-shock; for carbonated, ISO 7458 internal-pressure testing.
  • Embed recyclability labelling logic into artwork checklists.

2) Definitions & Concepts

  • 2‑piece can (DWI/DRD): Drawn body with integral base; separate end after fill.
  • 3‑piece can: Welded side seam + two ends.
  • Double seam: Five‑ply interlock + sealing compound (hermetic).
  • BPA‑NI: No intentional BPA; verify NIAS via migration testing.
  • Hot‑end/Cold‑end coatings (glass): Tin‑oxide layer + polymeric layer for scuff resistance and label adhesion.
  • BVS (ROPP) finish: Deep screw finish for still wines; not for high‑CO₂ unless designed for it.

3) Standards, Regulations, Governance

United States
  • Coatings: 21 CFR 175.300; adhesives 175.105; gaskets 177.1210.
  • Processing controls: 21 CFR Parts 113 (LACF) and 114.
European Union
  • Framework 1935/2004; GMP 2023/2006.
  • BPA in varnishes/coatings: Reg. (EU) 2018/213.
  • Tinplate/ECCS: EN 10202.
United Kingdom
  • Retained EU FCM approach; FSA materials guidance.

4) Evidence Base & Benchmarks

  • Aluminum can bodies: 3004/3104‑H19; ends/tabs 5182‑H48/H19 (supplier variants exist).
  • Steel (tinplate/ECCS) per EN 10202:2022; double‑reduced grades for DRD.
  • Glass internal pressure: ISO 7458; ASTM C147 alternatives.
  • Glass thermal shock: ASTM C149.
  • Finishes/closures: ISO 12821 (crowns), EN 17177 (crowns), EN 16293 (BVS).
  • Glass surface treatments: hot‑end + cold‑end levels affect labels.
  • Coatings: BPA‑NI polyester/acrylic growing; validate via migration and pack tests.
  • Gaskets/plasticizers: ESBO SML 60 mg/kg; 30 mg/kg infant foods (EU).

5) Design & Production Implications

  • Match lacquer to product chemistry & process; verify 21 CFR / EU migration.
  • Lock glass finish early: carbonated → crowns (ISO/EN) with ISO 7458 burst targets; still wine → BVS (EN 16293 + CETIE Guide 6).
  • Hot‑fill/pasteurization: specify ASTM C149 ΔT and lug closure liner vacuum performance.
  • Double seam reliability dominates in cans—sampling plan and compound weight targets by diameter.
  • Decoration: metal—offset litho + retort‑capable OPV if needed; glass— ACL for heat; organic UV for cold‑fill; perforate sleeves.

6) Sustainability & Compliance

  • Use current How2Recycle/OPRL label logic; aerosols vary.
  • Design for glass sorting: perforated sleeves; washable inks.
  • Claims: prefer “BPA‑NI coating, migration verified …” over “BPA‑free”.
  • EPR: declare component weights; keep coating/label specs for fees.

7) Workflow & Tooling

  • Print‑ready (metal): dielines with seam allowances; OPV callouts; compound window; 175.300 statement; alloy/temper callouts.
  • Glass pre‑press: label adhesion test on coated glass; perforated sleeves; finish & torque; C149 ΔT; ISO 7458 burst if carbonated.
  • Compliance: migration plan (EU/US), EuPIA inks CoC, ESBO SML checks for infant foods.
  • Recyclability: label decision and sleeve‑removal instruction.

8) Category‑Specific Guidance

  • Beverage (carbonated): crown per ISO 12821/EN 17177; ISO 7458 burst margin; pasteurization profile; ACL inks.
  • Food (retort cans): lacquer per chemistry; seam integrity/compound weights; 21 CFR 113/114 records.
  • Beauty: organic inks often sufficient; confirm EuPIA & adhesion on glass cold‑end coating; avoid sleeves that hinder sortation.

9) Common Pitfalls & Red Flags

  1. Assuming glass always suits carbonation without ISO 7458 tests.
  2. Full‑body sleeves without perforations on glass.
  3. Non‑retort inks/OPV on retorted metal.
  4. Insufficient hot‑/cold‑end coating → label lift/scuff.
  5. ESBO SML exceedances on infant foods from PVC plastisols.
Designer tip: Ask suppliers for coating system IDs, BPA‑NI statement, and migration reports under your conditions of use. Store with artwork approvals.
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