Food Jars: Wide Mouth, Tamper Evidence and the Filling Problem
By Joe Joo · 8PCK · Shantou · Updated 26 October 2026
A food jar is chosen by the filling line before the shelf: how wide the mouth is decides how fast you can fill, and how you close it decides whether the customer trusts it.
Food jars look simple and are decided by three things: the mouth diameter, the closure, and whether the product is hot or cold when it goes in. Get those right and the rest is decoration.
We mould 250 ml and 500 ml PET food jars with 63 mm and 70 mm mouths, and quote PP where hot filling or chemical resistance demands it.
The free Bottle Spec Checker tests whether your neck fits the closure and whether the wall survives a pump stroke.
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Wide Mouth vs Narrow Mouth
A wide mouth fills faster and takes a spoon; a narrow mouth pours. For spices and powders, wide mouth with a sifter insert; for honey and sauces, narrow with a controlled-flow cap.
The mouth also sets the tamper-evident options: induction seal liners need a flat land on the rim, and not every jar design has one.
Hot Fill and Why PET Has a Ceiling
Standard PET softens above roughly 60 °C. For jams and sauces filled hot, PP is the safer material and the lower in unit cost answer overall — even though the jar looks less premium in clear.
We would rather quote PP and keep the line running than sell a PET jar that distorts on your filler.
Tamper Evidence That Actually Gets Used
Induction seal liners are the default for food: they leave a visible membrane and are obvious if broken. Pressure-sensitive liners are easier to apply but easier to reseal unnoticed. For export markets where the retailer audits the pack, induction is the safer conversation.
Where Food Jars Fail
Food packaging failures are seal failures, not shape failures. Three to check before the carton is printed.
Induction Seal Needs a Flat Land
The foil seals to a flat rim. A decorative rim with a 1 mm land will not hold, and no torque fixes it. Check the rim width on the drawing.
Hot Fill Distorts Standard PET
Above roughly 60 °C, standard PET deforms. For jam and sauces we quote PP, even though clear PET looks better on shelf.
Vacuum Pull on Cooling
A hot-filled jar cools and pulls a vacuum; a thin wall collapses inward. PP with a thicker wall handles it, PET does not.
What Documents a Food Buyer Should Ask For
The resin declaration of compliance, and a migration test on the finished article where the destination market requires it. For export to the EU, the declaration must reference EU 10/2011 and the specific monomer limits.
Ask per batch, not per product family — the resin lot is what the declaration covers.
Questions We Get on This
Are your food jars food-contact certified?
The PET grades carry an EU 10/2011 declaration per order; we hold a migration test on PE grades and a RoHS verification. Ask for the document that matches the exact grade you buy.
Can I put jam in a PET jar?
Only if it is filled cold. Hot jam above about 60 °C needs PP, or a heat-set PET we do not offer.
Do you supply the lid with the jar?
Yes — screw caps, induction liners and sifter inserts, matched to the mouth.
Can the jar be square instead of round?
Square footprints stack better and are available in the 500 ml size; round is standard for 250 ml.
Can PET jars be used for hot fill?
No for standard PET above about 60 °C. PP or heat-set PET is the answer.
Do you supply induction seal liners?
Yes where the rim has a flat land wide enough for the seal.
What MOQ applies to food jars?
1,000 pcs per colour on stock moulds.
Sizes That Fit This Guide
Get a Price on This, Within One Business Day
Tell us the capacity, the neck and the quantity. You get unit price, lead time and a sample plan — not a catalogue.
Every batch is gauged at the neck and weighed. The documents travel with the shipment.