Packaging OTR and WVTR Barrier Testing FAQ

Data: ASTM International publishes oxygen and water vapor transmission test methods that let a brand measure OTR and WVTR under controlled conditions on a shared measurement basis.

Judgment: Require the named method and test conditions behind any barrier number, because a transmission value without its method and conditions cannot be repeated or compared.

Source: ASTM International - ASTM Standards (2024)

Data: ISO's standards catalogue covers the barrier and transmission test standards that OTR and WVTR specifications draw on, giving a common language between brand and supplier.

Judgment: Write the method and acceptance limit into the specification, because an agreed method and limit are what make a barrier number enforceable in a supply relationship.

Source: ISO - ISO Standards Catalogue (2024)

Data: TAPPI publishes technical resources on paper and packaging barrier properties, including the material and coating data that OTR and WVTR performance depends on for fibre-based formats.

Judgment: Anchor barrier expectations to the material's technical data and the coating system, because a fibre format's OTR and WVTR are set by the substrate and coating, not by intent.

Source: TAPPI - Paper and Packaging Technical Resources (2024)

What do OTR and WVTR measure?

OTR is the oxygen transmission rate, the amount of oxygen passing through a material over time, and WVTR is the water vapor transmission rate, the amount of moisture passing through. They are the two barrier properties that decide whether a product oxidises or goes stale, and whether it dries out or absorbs moisture. They are measured under controlled conditions with a named method, so the conditions and the method must be stated with the number.

How do you read a barrier data sheet correctly?

Check the method and the test conditions first — temperature, relative humidity, and which gas — because an OTR or WVTR number without its conditions cannot be compared to another. Then check whether the value is for flat material or a formed pack, since a flat-sheet value describes the substrate and not the finished pack with its seals and corners. Use the data sheet to screen candidates, then verify on the formed pack.

Why do test conditions matter so much?

Because transmission values are condition-dependent, and the conditions decide what the number means. Two WVTR numbers measured at different relative humidity are not comparable, and transmission generally changes with temperature. State the method, the temperature, the relative humidity, and the sample form before you compare any two values, or the comparison is meaningless.

What is the difference between flat sheet and formed pack?

A flat-sheet value describes the substrate, while a formed pack adds seals, folds, corners, and closures that transmit differently. A format can have an excellent substrate OTR and still fail on a weak seal, which is why the formed pack, not the sheet, is what matters for a real product. Use the flat value to screen candidates, then verify on the formed pack.

How do you set a barrier specification?

State the OTR and WVTR limits the product needs, the test method, and the conditions, then write those limits into the specification so the supplier designs and verifies against them. The limit comes from the product's sensitivity, not from what a material family typically achieves. An agreed method and acceptance limit turn a barrier dispute into a shared measurement, so both belong in the spec.

What are the most common barrier testing mistakes?

Comparing values measured under different conditions, mixing up flat-sheet and formed-pack numbers, not naming the method, failing to set an acceptance limit, and leaving the seal untested. Each is a measurement or specification gap rather than a material failure, so it is avoidable before the test runs. Fix the conditions, name the method, state the sample form, set the limit, and test the seal.