CO2 loss (carbonation retention)

What you will see

CSD bottles lose CO2 over storage at a rate exceeding 17% over the validated shelf life (industry standard). Bottles arrive at retail "flat" or with low fizz. May or may not show visible leakers — the loss can be slow + diffuse through a partially-compromised seal. Diagnosis is CROSS-COMPONENT: the root cause can be on the closure side (sealing surface, brittleness, thread defect), capper side (torque, angle, downforce), OR preform side (sealing land damage, neck wall thickness undersize, ovality). The diagnosis flow below isolates which component is responsible.

Likely causes

• [CLOSURE-SIDE] Sealing surface defect (IMD STATION 05 escape; scratch on seal land)
• [CLOSURE-SIDE] Pinhole / micro-perforation (IMD STATION 06 escape)
• [CLOSURE-SIDE] Brittleness from over-drying or rPET imbalance (micro-cracks during application)
• [CAPPER-SIDE] Insufficient application torque
• [CAPPER-SIDE] Application angle deviation > 2° (uneven seal compression)
• [CAPPER-SIDE] Chuck wear / cocked application
• [PREFORM-SIDE] Bottle finish top sealing surface damage (scratches/nicks)
• [PREFORM-SIDE] Neck wall thickness undersize (neck flexes under cap downforce, seal moves)
• [PREFORM-SIDE] Neck ovality > 0.15 mm
• [ENVIRONMENT] Storage temperature exceeds product spec — accelerates loss but not a defect

Do this first

STOP shipping the affected lot. Quarantine pending diagnosis. Run a 24h CO2 retention test on 30 bottles from the suspect lot vs 30 bottles from a known-good lot. If retention loss is confirmed, proceed with cross-component diagnosis below.

How to diagnose it

1. == STEP 1 — Quantify the failure ==
2. 24h, 7d, 14d CO2 retention measurements on 30 bottles. Target: <1.0 vol loss at 14d for CSD
3. Removal-torque drop test: measure break torque at 0h, 24h, 7d. Drop >40% indicates seal compromise
4. == STEP 2 — Isolate the component ==
5. A) Swap to a DIFFERENT closure lot (same SKU). Re-run 24h test. If leakers stop → closure-side
6. B) Swap to a DIFFERENT preform lot (same SKU). Re-run 24h test. If leakers stop → preform-side
7. C) Re-align + re-calibrate capper (angle ≤2°, torque mid-window). Re-run. If leakers stop → capper-side
8. == STEP 3 — Confirm root cause ==
9. [CLOSURE-side confirmed] Inspect sealing surface (IMD STATION 05 simulation: angled-light visual on inverted closures). Backlight inspection for pinholes (STATION 06)
10. [CAPPER-side confirmed] Measure application angle with digital gage (must be <2°). Measure torque with calibrated torque wrench (must be in SKU window). Inspect chuck face wear
11. [PREFORM-side confirmed] Invert preforms; inspect top sealing surface under angled light. Section 5 preforms; measure neck wall thickness at sealing area (must meet SKU spec: PCO 1881 1.6-2.2 mm, PCO 1810 2.0-2.6 mm). Measure neck OD at 0° and 90° for ovality

How to fix it

1. Quarantine the affected lot — do not ship until root cause is identified and corrected
2. Once isolated (Step 2 above), apply the specific remediation for that component:
3. Step 2a: Closure-side → contact Delta with photos + CO2 retention data; Delta investigates IMD escape on the source mold cavity; replacement lot from validated cavities
4. Step 2b: Capper-side → adjust angle / torque / chuck; revalidate with 30-bottle CO2 test
5. Step 2c: Preform-side → contact Delta with photos + measurements; Delta cavity inspection; replacement preform lot
6. After remediation, run a 30-bottle validation: 24h + 7d CO2 retention must be within SKU spec
7. Document the entire investigation in the QA log (root cause, evidence, remediation, validation) for traceability + audit-ready packaging