WVTR – ASTM F1249

What Is WVTR — ASTM F1249?

The WVTR test measures the amount of water vapour passing through a film per unit area and unit time. The film is placed in a cell with different humidity on each side; the vapour passing through is either continuously monitored by a sensor or determined by the weight gain of a desiccant. The result is given in g/m²/day.

Purpose of WVTR — ASTM F1249

The purpose is to numerically determine the packaging's moisture-barrier function and provide data for the product's shelf-life calculation. Food that absorbs moisture goes stale; food that loses moisture dries out; in pharmaceuticals, moisture degrades active substance stability.

Which Products Is WVTR — ASTM F1249 Applied To?

Flexible packaging films
Metallised and barrier-coated films
Blister foils
Laminate structures
Paper and board barrier coatings

In Which Sectors Is WVTR — ASTM F1249 Used?

PackagingLogisticsRetailFoodPharmaceuticalsElectrical & Electronics

Standards Related to WVTR — ASTM F1249

ASTM F1249water vapor permeability (WVTR) test

WVTR — ASTM F1249 Conditions

Temperature and humidity: Conditions defined in the standard; 23 °C/50% and 38 °C/90% are commonly used
Reporting the condition: The result is not meaningful without stating the measurement condition
Equilibrium: The measurement continues until a steady transmission rate is reached

Equipment for WVTR — ASTM F1249

WVTR tester (infrared or humidity sensor type)
Gravimetric cup assemblies and desiccant
Climate chamber
Precision balance

Sample Requirements for WVTR — ASTM F1249

Flat film specimens free of holes, wrinkles and fold marks
The specimen must fully cover the instrument's cell
Film thickness and layer structure must be provided
Which direction the barrier layer faces must be stated

Duration of WVTR — ASTM F1249

The measurement runs until a steady transmission rate is reached; this takes markedly longer for high-barrier films, since the amount of vapour passing through is very small and reaching equilibrium takes time.

WVTR — ASTM F1249 Procedure

1The specimen is cut and placed in the cell without leaks.
2The defined humidity difference is created on the two sides of the cell.
3Temperature and humidity are brought to equilibrium.
4The water vapour passing through is monitored by sensor or by weight gain.
5The value is recorded once a steady transmission rate is reached.
6The result is calculated in g/m²/day.

WVTR — ASTM F1249 Acceptance Criteria

The acceptance criterion is the maximum WVTR value in the specification. The limit is set according to the product's moisture sensitivity and target shelf life; the standard does not define a limit.

Evaluation of Results

The result is only meaningful together with the measurement condition: a value measured at 38 °C/90% can be multiples of the value at 23 °C/50%. Film measurement also does not show packaging performance; seal areas and the lidding film determine the package's real barrier.

WVTR — ASTM F1249 Report

Specimen identification, thickness and layer structure
Measurement temperature and relative humidity condition
Standard and method applied
WVTR result (g/m²/day) and measurement uncertainty
Barrier layer orientation

Accreditation

EUROLAB holds internationally recognised accreditation obtained from accreditation bodies party to the IAF and ILAC multilateral recognition arrangements, under ISO/IEC 17025 for laboratory testing, ISO/IEC 17020 for inspection and surveillance, and ISO/IEC 17021-1 and ISO/IEC 17065 for system and product certification. This chain ensures the reports and certificates issued are accepted worldwide.

Whether this test can be offered within accredited scope depends on your product and the standard applied; since accreditation is method-based, the scope is confirmed in writing at the quotation stage.

Scope and authorisations

Related Regulations

(EC) 1935/2004 Regulation on Materials Intended to Come into Contact with Food

Ambalaj Testleri — What Does This Testing Field Cover?

The section below describes the field that the WVTR test belongs to; the conditions and acceptance criteria of this particular test are given in the sections above. The scope specific to your product is confirmed in writing at the quotation stage.

Packaging testing examines two different functions separately: does the packaging protect the product during transport, and does the packaging material transfer harmful substances into its contents? These two questions require different laboratory infrastructure and must not be confused.

On the protection side, distribution simulation is carried out: drop, vibration, compression, stacking and, where needed, low pressure tests are applied in sequences representing the real shipping chain. These tests are meaningful as a SEQUENCE rather than individually; in real life too, packaging is exposed to successive loads and each load builds on the damage left by the previous one. Specifications such as ISTA and ASTM D4169 define these sequences by shipment type.

The shipment type determines the sequence itself. The exposure of a palletised load differs from that of a parcel shipped individually: the latter sees far more handling, more drops and impacts in a wider variety of orientations. The growth of e-commerce has brought this second scenario to the fore and turned parcel shipping simulation into a specification group of its own.

On the food contact side, MIGRATION is what counts: the amount of substance passing from the packaging material into the food is compared against overall and specific migration limits. For plastic packaging the list of permitted substances and the limits are defined in separate legislation; the declaration of conformity (DoC) rests on this assessment and is a document that every link in the supply chain must carry.

In a migration test the choice of SIMULANT is critical. Because testing with real food is not practical, liquids representing food are used: different simulants for aqueous foods, for fatty foods and for acidic foods. Choosing the wrong simulant invalidates the result; the choice depends on which food type the packaging will contact and at what temperature.

Barrier properties are a third axis. Oxygen and water vapour permeability directly determine the shelf life of the product; in pharmaceutical and food packaging these values are a design input. Barrier performance is sensitive to temperature and relative humidity, so the measurement conditions are part of the report.

Sterile medical device packaging is the most tightly regulated sub-body of this family. Here the packaging is a barrier maintaining sterility; seal strength, leak testing, distribution simulation and shelf-life studies run together as a validation package.

The packaging legislation side is becoming rapidly more demanding. Recyclability, recovered content ratio, packaging reduction and reuse targets must now be measurable and declarable; this turns packaging design from a material selection exercise into a conformity exercise.

Method groups in this field

Distribution simulation
Drop, random and fixed frequency vibration, compression, stacking, low pressure; as ISTA and ASTM D4169 sequences.
Mechanical strength
Edge crush (ECT) in corrugated board, bursting strength, box compression strength, tape peel adhesion.
Barrier measurements
Oxygen transmission rate (OTR), water vapour transmission rate (WVTR), permeability in film and sheet materials.
Migration
Overall and specific migration tests; simulant and temperature conditions are chosen according to the use scenario.
Seal and integrity
Seal peel strength, leak detection by dye penetration, bubble test, headspace analysis.
Shelf life
Real-time and accelerated ageing; part of the validation package in sterile packaging.

Commonly confused in this field

A single drop test is not a distribution simulation; the tests are applied as the sequence defined in the specification.
A migration test carried out with the wrong simulant or the wrong contact temperature is invalid.
Accelerated ageing does not replace real-time ageing; a shelf life claim is supported by real-time data.
Barrier values are valid together with the measurement temperature and relative humidity; an OTR/WVTR value given without conditions cannot be compared.
A packaging change (film supplier, seal parameter, box design) may require the validation to be repeated.
A food contact declaration of conformity is not a test report; it is a document that rests on reports but summarises a broader assessment.

Which decisions these results support

Reducing shipping damage and verifying the packaging design
Declaration of conformity for food contact packaging
Supporting the shelf-life claim
Validation of sterile device packaging
Recyclability and content declarations under packaging legislation

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Frequently Asked Questions About WVTR — ASTM F1249

We got different results from different labs — why?

The most common reason is a different measurement condition. WVTR is highly sensitive to temperature and humidity; a value given without stating the condition cannot be compared. A difference in method (sensor/gravimetric) can also create a difference.

Does the film result give the package's shelf life?

Not directly — it is an input to the calculation. The package's real moisture transmission depends on the film area, seal areas, lidding film and any closure system. A shelf-life study assesses these together.