LeapPlastic Clamshell Packaging — PET & RPET Clear Containers
A Clamshell Has to Do Four Things at Once
A plastic clamshell is a one-piece hinged container that must protect the product, show it clearly, vent what needs venting and close reliably at speed. Those four requirements pull against each other: thicker material protects better but costs more and reflects light; tighter closures travel better but slow packing; more venting controls condensation but dries the product.
Clamshell food packaging is specified against fill weight, temperature and display conditions. Most clamshell failures we see are specification failures, not material failures — a 0.25 mm berry punnet specified for a 500 g fill, a hinge that cracks at the fold, or an anti-fog coating that was never specified for a refrigerated case. This page sets out the specifications that decide performance, by application.
PET, RPET, PP or PLA — Choosing the Material
| Material | Clarity | Temperature | Recyclability | Best for |
|---|---|---|---|---|
| PET | 88–92% light transmission | −20°C to 60°C | Widely recycled (code 1) | Berries, produce, deli, cold display |
| RPET | 85–90%; near-virgin at higher grades | −20°C to 60°C | Widely recycled; GRS certified options | Retail programs with recycled-content targets |
| PP | Translucent to opaque | −20°C to 120°C | Recyclable where rigid PP is collected | Hot fill, microwave, takeaway |
| PLA | Clear but hazes over time | −20°C to 85°C | Industrially compostable where certified | Cold food with a compostable claim |
For fresh produce, PET and RPET are the practical default: they are the clearest, the most widely recycled and the easiest to specify against retail packaging scorecards. PLA is a compostable option but not a like-for-like substitute — it hazes faster, has a lower heat ceiling and is not accepted in most plastic recycling streams.
Formats & Typical Sizes
| Format | Typical size | Material thickness | Common use |
|---|---|---|---|
| Berry punnet | 1 pint / 1 lb / 250–500 g | 0.18–0.40 mm | Blueberries, strawberries, cherry tomatoes |
| Produce clamshell | 500 g – 2 kg | 0.30–0.60 mm | Grapes, figs, specialty fruit, cut vegetables |
| Deli / bakery clamshell | 500 ml – 2 L | 0.30–0.50 mm | Salads, pastries, sandwiches, prepared food |
| Large retail clamshell | 2–5 L | 0.50–0.80 mm | Family packs, bulk produce, e-commerce |
Thickness is specified against fill weight and stacking height, not by habit. A 0.25 mm punnet is right for 250 g of blueberries and wrong for 500 g of grapes; a 0.35 mm RPET punnet is the common choice for a 1 lb strawberry pack that must survive retail stacking. See the berry container guide for fruit-specific sizing. The same clear-box logic applies to cut flowers — see floral & bouquet packaging.
Specifications That Decide Performance
| Specification | Why it matters | What to specify |
|---|---|---|
| Hinge design | The fold is where clamshells crack first, especially at low temperature | Living hinge with a minimum 0.3 mm web; test at −18°C if frozen |
| Closure | Loose lids open in transit; too tight slows packing | Snap lock with an audible close; specify opening force for automated lines |
| Venting | Controls condensation and ethylene for produce | Vent area by product: berries need more than cut fruit; mushrooms need the most |
| Anti-fog | Condensation obscures the product in refrigerated display | Anti-fog on the lid, not the base; verify 72-hour clarity at 4°C |
| Dimensional tolerance | Affects automated denesting and case packing | ±2 mm on plastic; confirm against your filling line |
| Material thickness | Balance of protection, cost and weight | 0.18–0.40 mm berries; 0.30–0.60 mm produce; 0.50–0.80 mm large packs |
Compliance, Recyclability & the 2026 Rules
PET clamshells for food contact must meet FDA 21 CFR 177.1630 in the US, and EU 1935/2004 with 10/2011 in Europe. For RPET, the recycling process itself must be evaluated for food contact — an FDA Letter of No Objection or an equivalent EFSA-evaluated process. Recycled content from an unevaluated stream is not food grade, whatever the feedstock.
Two regulatory changes are reshaping clamshell specifications. The EU's BPA restriction (Regulation (EU) 2024/3190) applies from 20 July 2026 and reaches beyond polycarbonate to other bisphenols and derivatives — so inks and adhesives must be checked, not just the resin. And PPWR design-for-recycling rules favour mono-material PET/RPET packs with water-soluble labels and no mixed-material inserts. A clamshell that hits both is a simpler compliance story than a compostable alternative that no local stream collects.
GRS-certified RPET is available for buyers with recycled-content targets; see plastic packaging for the full material range and food grade packaging for the documentation set.
Plastic Clamshells — Frequently Asked Questions
What is clamshell food packaging used for?
A clamshell is a one-piece hinged container used where the product must be visible and protected at the same time: berries and produce, deli and prepared foods, bakery, and grab-and-go meals. It replaces a separate base and lid with a single moulding, which reduces packing steps and eliminates mismatched lid sizes.
What thickness should a berry clamshell be?
Berry punnets commonly run 0.18–0.40 mm, with 0.35 mm RPET a frequent choice for 1 lb strawberry packs that must survive retail stacking. A 250 g blueberry punnet can go thinner than a 500 g grape clamshell. Specify against fill weight and stack height, and test a full pallet rather than a single box.
Is PET or RPET better?
RPET is the better default where a recycled-content claim matters and the grade is food-contact approved; modern food-grade RPET is close to virgin PET in clarity. Virgin PET remains slightly clearer and is simpler to specify where recycled content is not required. Both are recyclable in the same stream, which keeps the end-of-life story simple.
Can clamshells be compostable instead?
PLA clamshells exist and are industrially compostable when certified, but they are not a drop-in replacement: they haze over time, have a lower heat ceiling and are not accepted in most plastic recycling. If your market has no industrial composting access, a PET/RPET clamshell is usually the more defensible pack. See compostable packaging for the trade-off.
What is the MOQ for custom clamshells?
Stock sizes start at 5,000 pieces. Custom cavity shapes require a new thermoform mould and typically start higher, depending on size and cavity count; tooling is quoted per project. Custom printing is normally done on a sleeve or label rather than directly on the clamshell, because print on the forming area disturbs clarity.
Do you supply anti-fog clamshells?
Yes — anti-fog treatment on the lid, which is where condensation obscures the product in a refrigerated case. Specify the display temperature and the required clarity duration; we verify 72-hour clarity at 4°C for standard grades and can quote higher-performance coatings for humid markets.
Need a clamshell specification?
Send your product, fill weight and stacking height — we will recommend a material, thickness and vent pattern.
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