How PET bottles, jars and closures are made
PET bottles and jars are made in two steps. A preform, a thick test-tube shape with the finished neck already moulded, is injection moulded. It is then reheated and stretch-blown into a bottle mould. The neck never changes after the first step, so neck defects come from the preform mould and body defects from the blowing. HDPE bottles are usually extrusion blow moulded from a hanging tube of plastic, which leaves a pinch-off line on the base. Caps and closures are injection or compression moulded from PP or HDPE, often with a tamper-evident band and a liner or sealing lip.
Indian makers supply bottles, jars and caps for cosmetics, personal care, food, pharmaceuticals and household chemicals, often to exporters who fill them in India, and sometimes empty to overseas fillers. Plastic packing articles (HS 3923) were US$1,208.7 million of exports in FY2025-26 (TradeStat, provisional), but that heading also includes sacks and bags, which make up more than half of it.
A bottle is a component, not a finished product. It must run on someone's filling and capping line, so dimensions matter more than looks.
What we check on rigid plastic packaging
| Check | How it is checked | What fails |
|---|---|---|
| Neck finish | Thread and neck diameters, height and support ring measured with callipers and go/no-go gauges against the drawing | Neck out of tolerance, ovality, damaged sealing surface |
| Capacity | Bottle weighed empty and brim-full with water; fill-point capacity where specified | Capacity outside tolerance |
| Weight and wall thickness | Bottles weighed; cut sections measured at shoulder, panel and base | Light bottles, thin spots, uneven material distribution |
| Closure fit and torque | Caps applied by hand or with a torque tester to the specified torque, then removed; tamper band checked | Caps stripping, too loose, tamper band breaking early or not breaking |
| Leak | Bottles filled with water, capped, inverted and squeezed; vacuum test where the factory has one | Leaks at the neck or base |
| Top load | Top-load tester reading where available, or witnessed at the factory's QC lab | Collapse below the specified load |
| Tethered cap | Cap opened and checked that it stays attached and allows drinking or pouring | Tether breaking on opening, cap getting in the way of use |
| Appearance | Bottles inspected against a light for clarity, specks, haze and gate defects; colour against standard | Black specks, haze, pearlescence, stress whitening, off-colour |
Common rigid plastic packaging defects and how they are classed
| Defect | Typical cause | Class |
|---|---|---|
| Contamination inside food or pharma bottles | Dirty storage, open bags, insects | Critical |
| Neck out of tolerance or damaged sealing surface | Worn preform mould, handling damage | Major (critical if it causes leaks of hazardous contents) |
| Leak at cap | Wrong cap and neck combination, liner missing | Major |
| Capacity out of tolerance | Wrong blow mould, shrinkage | Major |
| Thin walls or base | Light preform, poor heating profile | Major |
| Rocker bottom (bottle does not stand flat) | Base not formed properly | Major on filling lines |
| Black specks or haze | Degraded material, moisture in PET resin | Minor, major on clear premium packs |
| Scuffs and scratches | Bottle-to-bottle contact in bulk packing | Minor |
Your defect list decides the final class.
Market rules for plastic bottles, jars and closures
- Tethered caps, EU. Under Article 6 of the Single-Use Plastics Directive (EU) 2019/904, beverage containers up to 3 litres with plastic caps may only be placed on the market if the caps stay attached during use. This has applied since 3 July 2024. Glass and metal containers with plastic caps are excluded.
- Recycled content, EU. The same directive sets Member State averages for PET beverage bottles: at least 25% recycled plastic from 2025 and 30% for all beverage bottles from 2030. Under the Packaging and Packaging Waste Regulation (EU) 2025/40, from 1 January 2030 at the earliest, plastic packaging must contain minimum recycled content per manufacturing plant, for example 30% for contact-sensitive PET packaging and 35% for most non-contact-sensitive packaging.
- Other PPWR duties. The regulation applies from 12 August 2026. The heavy-metal limit (lead, cadmium, mercury and hexavalent chromium together not above 100 mg/kg) applies now; harmonised sorting labels follow from 12 August 2028 at the earliest. Manufacturers keep technical documentation and an EU declaration of conformity.
- Food contact. Bottles and jars for food need a declaration of compliance under Regulation (EU) 10/2011; recycled PET for food contact must come from an authorised recycling process under Regulation (EU) 2022/1616. In the US, FDA 21 CFR Part 177 covers the polymers. See EU 1935/2004 and FDA food contact.
- REACH. Colourants and additives must meet REACH restrictions. See EU REACH.
Packing, transit and your purchase order
Empty bottles are mostly air, so freight cost per bottle is high and factories are tempted to over-fill bags and cartons. Bottles packed loose in big polybags scuff each other and can deform at the neck. Bags must be closed against dust and insects, especially for food and pharmaceutical use. Heat in a closed container can distort thin PET and HDPE, and caps packed loose in bulk can be crushed. The inspector checks bag closure, carton strength, pallet stretch-wrap and that each lot is labelled with item, batch and quantity so the filler can trace it.
Put these in your purchase order:
- Drawings for bottle and closure with neck finish dimensions and tolerances.
- Brim-full and fill-point capacity, weight and minimum wall thickness.
- Application and removal torque for the closure and tamper band behaviour.
- Top-load requirement and leak test method.
- Material grade, colour, recycled content and the certificates behind it.
- Food-contact declaration and test reports where needed; tethered cap design for EU beverages.
- Packing: bags, layer pads, cartons or octabins, labels and pallet build.
Moulded containers sold to consumers are covered under plastic houseware. Book an inspection anywhere in India.
Sources
- Department of Commerce, TradeStat: commodity-wise exports (HS 3923, FY2025-26 provisional)
- Directive (EU) 2019/904 on single-use plastics (Articles 6 and 17, Annex Part C)
- Regulation (EU) 2025/40 on packaging and packaging waste (Articles 5, 7 and 12)
- Commission Regulation (EU) 2022/1616 on recycled plastic food contact materials
- 21 CFR Part 177, Indirect food additives: polymers (eCFR)