Preserve the test conditions and specimen identity when comparing water vapour transmission rate evidence. A WVTR number copied into a quotation is incomplete if the method, units or conditions disappear. Ask the qualified reviewer how the report relates to the proposed material and product. This guide gives procurement a moisture-evidence record without prescribing a universal barrier value or promising a particular storage duration.
Check the tested material and report scope
Identify the report source, sample description and relevant material revision. Ask whether the test article matches the proposed construction or only one component. A product description such as moisture barrier film does not establish the exact sample tested. If the package has distinct features or regions, ask how the evidence relates to the complete proposal. Keep original reports retrievable and record any supplier explanation separately. This preserves the difference between measured information and an interpretation offered during the sales discussion.
Preserve the measurement basis
Record method, temperature, humidity conditions, units and the reported result or limit as stated. ASTM F1249 is a standards-owner reference for one WVTR method. Its existence does not supply an acceptance limit for a particular food or other product. Ask the technical reviewer whether proposed comparisons use a compatible basis. Avoid mixing moisture transmission with oxygen transmission or treating their units as interchangeable. Where data is normalised or converted, preserve the original value and the responsible reviewer’s calculation basis.
Ask what the product needs
Provide the relevant product, proposed storage conditions and packing details to the technical owner. A low film result is not itself a completed qualification of the filled package. Seals, geometry and other interfaces need their appropriate evidence scope. AMETEK MOCON covers both film and package permeation testing. Use that distinction to ask the next question, not to invent a required test plan. The qualified team should determine suitable evidence and acceptance criteria for the actual product and intended conditions.
Build a moisture-evidence comparison record
Use one record for each proposed construction and supporting report. The format keeps procurement comparisons honest when suppliers present data on different bases.
| Record | What to capture and how to use it |
|---|---|
| Material and specimen | Record the proposed construction and the report's actual test article. Identify any difference and request clarification, rather than treating a shared barrier description as proof that both references cover the same material. |
| Conditions and method | Preserve the test method and stated temperature and humidity conditions. Ask the qualified reviewer to decide whether results are comparable before placing them in a ranked quotation table. |
| Value and units | Copy the result, units and limit notation accurately. Keep any conversion, normalisation or interpretation with its calculation basis and reviewer, preserving the original reported information for later verification. |
| Product requirement | Record the moisture-related product concern and intended storage conditions available for review. Let the technical owner define the acceptance basis rather than applying a universal threshold borrowed from another product. |
| Evidence gap | Identify missing conditions, identity or complete-package evidence and assign an owner. Record what further information is needed before acceptance, distinguishing a promising proposal from an approved application specification. |
Do not remove the conditions column to simplify a commercial spreadsheet. If the table becomes too wide, link the evidence record; simplifying the presentation should not change the meaning of a measurement.
Illustrative unlike report conditions
Two illustrative material proposals include WVTR data, but their stated humidity conditions differ. The buyer records the difference and requests technical interpretation rather than selecting the smaller number. It also asks whether the reports refer to the complete proposed constructions. The comparison remains open until those questions are resolved. No material is declared suitable and no storage duration is calculated, because the hypothetical figures alone would not establish either decision.
Identify which moisture movement is being assessed
Water-vapour transmission describes movement through the tested specimen under stated conditions. A product can be harmed by moisture entering or by moisture leaving, depending on its requirements. Ask the product owner to define the concern before selecting a target. “Moisture proof” is too broad to establish the necessary evidence or a useful acceptance criterion.
The current ASTM F1249 catalogue identifies a modulated-infrared-sensor method for plastic film and sheeting. Its scope is a method reference, not a finished-pack guarantee. Record the actual report method and specimen rather than assuming that every figure labelled WVTR was obtained in the same way.
Preserve both sides of the condition
Locate the temperature, humidity conditions and relevant conditioning information on the report. Keep them beside the measured value. A humidity difference drives the tested transfer, so a percentage without its context is incomplete. If the report's description is unclear, ask the laboratory or supplier to clarify which condition applies to which side.
Compare candidates only after the technical reviewer confirms that the methods and conditions support the comparison. Do not rank two genuine values merely because one is numerically smaller. A report from a different temperature or humidity arrangement may answer a different question. The useful next step can be a comparable report rather than a premature material choice.
Read the units as part of the claim
Separate area-normalised film units, such as g/(m²·day), from whole-package units such as g/(package·day). Record any inequality or reporting limit exactly. “Less than” does not mean zero, and an absent unit cannot be inferred safely from the size of the number. Ask the source owner to resolve it.
For an illustrative film rate of 1 g/(m²·day) over 0.04 m², multiplication gives 0.04 g/day under the same simplified conditions. Over ten days, that arithmetic gives 0.4 g only if the assumed rate remains applicable throughout. The invented example demonstrates unit handling; it does not predict real product moisture gain, loss or shelf life.
Connect moisture evidence to the finished geometry
A flat specimen can help screen material candidates. The complete pack adds closures, folds and other relevant features. Ask what evidence is needed for those interfaces and for the intended handling. A film value alone cannot establish that every formed package retains the same effective barrier after converting and distribution.
AMETEK MOCON's whole-package paper compares five pouch candidates at 37°C; its WVTR tests used 100% RH test gas. Finished-package results exceeded flat-film predictions in the reported case. The paper's sample constructions and defects limit transfer to another project, so use the finding to frame the evidence level required.
Ask the product owner what change matters
The packaging team needs a product requirement, not just a desire for the lowest available number. Record the relevant product sensitivity information and proposed storage conditions. A technical team may need product studies or other evidence to relate moisture movement to an acceptable outcome. Do not invent a moisture threshold or storage duration to make the brief appear complete.
If the product formulation or quantity changes, ask whether the earlier requirement remains applicable. The same package can present a different product-to-package relationship. Keep that review connected to the complete construction and declared use rather than assuming that a successful material comparison covers every product variant.
State the next evidence request precisely
Where a supplier offers an alternative test condition, ask the technical reviewer whether it answers the same question. Keep the offered condition in the record even if another assessment is requested, so the reason for the additional evidence remains understandable.
Write whether the current report is applicable, not directly comparable or incomplete, with the reason. A useful request might seek the same method and conditions for the proposed construction or clarification of a missing unit. Another might concern the finished-package evidence selected by the technical owner.
Retain the original report and its interpretation separately. This lets procurement compare supplier responses accurately while preserving the technical basis. The completed record should explain what the reported WVTR means for this decision, what it does not yet establish and which evidence will close the remaining gap.
WVTR discussion: a practical specification example
Two samples have similar appearances but different material requirements. One may use a clear panel and another an opaque surface; neither appearance specifies its complete layer structure. Keep the product, storage conditions, fill method and required performance in the brief. Ask for the proposed construction in writing so the comparison remains meaningful when a paper-look or metallic appearance is introduced.
For this decision, start with the moisture concern and intended storage conditions. The useful output is the quoted water-vapour-transmission result with its test conditions. Put that output beside the relevant quotation, drawing or sample rather than leaving it in a separate email. This is an illustrative decision exercise, not a report of a completed customer trial.
Product references to make the discussion concrete
The catalogue includes clear-front opaque-back pouches and kraft paper pouches. These examples show different physical constructions; they are not interchangeable specifications. A clear front shows the contents while an opaque or metallic back provides a contrasting panel. Specify which face carries the principal artwork and check how it reads through the transparent face. The windowed side and opaque side need a coordinated material brief.
| Format reference | Material or construction to clarify | Details to include in the brief |
|---|---|---|
| Clear-front opaque-back pouches | Transparent front paired with opaque or foil-look back panels; confirm the layer construction on each face. | Front and back material requirements; artwork side and orientation. |
| Kraft paper pouches | Kraft or paper outer with a product-specific inner construction; paper appearance does not establish a plastic-free composition. | Paper colour and surface preference; full layer structure and thickness. |
Use the reference pictures to identify the base, side panels, window or opening that you mean. A picture cannot supply the missing dimensions or material layers. If a photograph shows a finish or closure you do not want, state that difference explicitly; otherwise a visual reference can introduce an unintended requirement.
Complete the record before requesting the next sample
- Attach the quoted water-vapour-transmission result with its test conditions. Identify the product or SKU and the date of the observation.
- Record the moisture concern and intended storage conditions. Keep confirmed information separate from proposed values and questions for the supplier.
- Add the actual fill weight or volume, the dimension convention, material proposal and intended closure. Include the number of designs and quantity per design when requesting a quotation.
- State which question the next drawing, sample or quotation must resolve. A change of size, closure or material should remain visible alongside the earlier reference.
This record makes the next conversation specific. It lets the design, purchasing and packing teams work from the same proposed item and shows which decision still needs evidence. Review the related product pages for format details, or prepare a custom packaging brief with the unresolved requirements.
Carry contextual data into the enquiry
Send the comparison record with the intended product and filling brief. Request the exact proposed material reference and supporting report scope. Keep the accepted evidence linked to the item revision and reassess applicability after a material or process change. This allows procurement to ask precise moisture-barrier questions without taking over specialist testing or qualification decisions.
Send the completed moisture-evidence comparison record with your product and filling details to Navkar Poly Print for a project-specific discussion. Ask for the proposed specification, evidence required and open questions to be recorded before quotation approval.
Sources and scope.
These references support the technical discussion. Product photographs illustrate formats; the material, dimensions and suitability of the proposed pack are confirmed for each project.
- ASTM F1249 water vapour transmission rate
Standards-owner method scope, distinct from an application-specific acceptance limit.
- AMETEK MOCON permeation testing
Instrument-manufacturer context for film and package permeation; product qualification requires appropriate scope.
- Shelf Life and the Importance of Testing the Whole Package
April 2024 manufacturer case paper; five-material pouch case, WVTR at 37°C/100% RH, no universal or Navkar result.
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