Leak-resistant describes performance under stated conditions and accepts that limits exist. Leak-proof sounds absolute unless the claim defines the liquid, temperature, duration, orientation, handling and acceptance criteria. For procurement, use measurable conditions rather than either label alone.

A universal guarantee is not appropriate. Performance changes with the food, free liquid, oil, heat, time, fill level, closure, tilting and physical damage. A supplier can evaluate a defined package against an agreed protocol, but that result should not be extended beyond the tested conditions.

The coating or barrier matters, but cut edges, pinholes, creases, folded corners, glue seams, locking tabs, lid fit and vents can be equally important. Evaluate the complete converted box, not only a flat material sample.

No. Grease-resistance methods such as the TAPPI kit test evaluate resistance to particular oil and grease mixtures on paper. They do not by themselves establish containment of water, sauce or free liquid through a completed box and its seams.

Temperature can change viscosity, condensation, paper stiffness, coating behaviour, adhesive bonds and closure fit. Buyers should specify filling temperature, holding time, refrigeration or freezing, reheating and expected delivery time, then test those conditions.

Vents can release steam and may reduce condensation for some foods, but they also create openings and can allow liquid to escape when the box tilts. Vent number and location should be selected with food quality, orientation and containment requirements.

No. Greater caliper may change rigidity, but it does not automatically seal edges, folds or seams and does not define the barrier layer. Board grade, coating, construction and converting quality must be evaluated together.

It can change how liquid is contained, but the liner or inner container must fit, remain closed and be suitable for the intended food-contact conditions. Buyers should evaluate the assembled system, including movement during delivery.

No. Food-contact compliance addresses chemical safety and regulatory suitability for intended use, while leak resistance is a physical performance question. Both evidence sets may be required, and neither substitutes for the other.

Agree on the real food or a justified test liquid, fill volume, temperature, contact time, orientation, closure method, handling steps and pass/fail criteria. Test production-representative printed and converted boxes, and include delivery or distribution simulation when relevant.

State the food and free-liquid content, oil level, fill temperature, holding and delivery time, expected tilting, refrigeration or reheating, closure, vents, target market and test requirement. Ask UGI Packging to confirm a suitable order-specific construction and sample plan without an undefined absolute claim.