Vapour Permeability in the Printing Industry

Measuring vapour permeability in the printing industry is important for several reasons, particularly when it comes to substrate performance, print quality, durability, and product functionality. Here’s a breakdown of the key reasons why it’s necessary:

 1. Substrate Selection and Performance
Many printed materials—such as packaging films, labels, and specialty papers—need to allow or block moisture transmission depending on the application. Measuring vapour permeability helps determine how suitable a substrate is.

• Low permeability: Needed for moisture-sensitive goods like food, pharmaceuticals, or electronics.
• High permeability: Useful for applications like breathable labels or compostable packaging.

2. Ink Performance and Drying
Ink and coating systems interact with the substrate. Vapour permeability affects:

• Drying speed: Too much permeability can cause overly fast ink drying, affecting adhesion.
• Ink setting: Helps avoid smudging or improper bonding to the substrate.
• Print clarity: Reduces the risk of bleeding or feathering on porous materials.

3. Packaging Requirements
In flexible packaging (a key area of printing), vapour permeability is often critical:

• Prevents moisture ingress or egress depending on product needs.
• Helps comply with shelf-life requirements.
• Necessary for modified atmosphere packaging (MAP) where gas and vapour control is essential.

4. Sustainability and Material Innovation
With the rise of biodegradable and recyclable materials, understanding vapour permeability is more important than ever:

• Many sustainable materials are more permeable to vapour and gas than traditional plastics.
• Testing is needed to ensure new materials meet industry standards.

 5. Regulatory Compliance and Standards
Some sectors require strict control of water vapour transmission (WVTR):

• ASTM F1249, ISO 15106-2, and other standards mandate WVTR tests.
• Essential for packaging compliance, especially in food safety and medical packaging.

 

Guide to typical water vapour transmission rates

Below is arough guide to typical water vapour transmission rates (WVTR) for key printing substrates and paper coatings, expressed in grams per square meter per day (g/m²/day) at standard test conditions (usually 38°C, 90% RH, ASTM F1249 or similar). Values can vary based on thickness, coating, and manufacturing method, but these are useful ballpark figures:

Uncoated Papers

Material	WVTR (approx.)
Newsprint	500–1000 g/m²/day
Uncoated wood-free paper	300–700 g/m²/day
Kraft paper (uncoated)	200–500 g/m²/day

• High permeability due to porosity.
• Absorbs and releases moisture easily—problematic for dimensional stability in printing.

Coated Papers

Material	WVTR (approx.)
Clay-coated (gloss/matte) paper	100–300 g/m²/day
Polyethylene (PE) coated paper	0.5–5 g/m²/day
Wax-coated paper	2–10 g/m²/day
Aluminum foil-laminated paper	<0.05 g/m²/day

• Clay coatings reduce permeability moderately.
• PE and wax coatings form effective moisture barriers.
• Foil laminates are nearly impermeable.

Flexible Packaging Films (common in printed packaging)

Film Type	WVTR (38°C, 90% RH)
Polyethylene (LDPE)	0.5–2 g/m²/day
Polypropylene (OPP)	0.2–1 g/m²/day
PET (Polyester)	1–3 g/m²/day
Nylon (PA)	5–10 g/m²/day
EVOH (high-barrier)	<0.1 g/m²/day
Cellophane (uncoated)	10–30 g/m²/day
Cellophane (PVdC-coated)	1–5 g/m²/day

 

• Films are often printed on one side and coated or laminated for barrier performance.
• EVOH and PVdC coatings offer excellent vapour barrier properties.

Biodegradable & Sustainable Materials

Material	WVTR (approx.)
PLA film (Polylactic Acid)	30–60 g/m²/day
Paper with bio-coating	50–200 g/m²/day
Compostable cellulose film	20–40 g/m²/day

• Generally more permeable than petroleum-based plastics.
• Needs careful evaluation for packaged product shelf-life.

 Notes on Testing:

• WVTR is highly temperature and humidity dependent; higher temperatures and RH increase permeability.
• Measurements are often performed at 38°C / 90% RH, but 23°C / 50% RH is also common in paper testing.

Advantages and disadvantages of different vapour permeability levels

Understanding the advantages and disadvantages of different vapour permeability levels is crucial for matching materials to printing applications. Here’s a clear breakdown for high, medium, and low vapour permeability across important use cases in the printing industry:

Vapour Permeability Levels

• High permeability: >300 g/m²/day
• Medium permeability: ~30–300 g/m²/day
• Low permeability: <30 g/m²/day

 1. Food Packaging
Low Vapour Permeability (Preferred)

• Benefits:
• Prevents moisture ingress or loss — extends shelf life.
• Protects contents from humidity (e.g., crisps, powdered milk).
• Essential for vacuum or modified atmosphere packaging (MAP).
• Disadvantages:
• Often requires multilayer or plastic/foil coatings — less sustainable.
• May impair recyclability or compostability.

🔴 High Vapour Permeability

• Risks:
• Rapid spoilage or texture degradation (e.g., soggy crackers).
• Condensation risks in cold-chain logistics.

2. Coated Paper (Magazines, Labels, Brochures)
🟡 Medium Vapour Permeability (Ideal)

• Benefits:
• Controls moisture balance — helps avoid paper curling or deformation.
• Allows moderate ink drying without excessive absorption.
• Improves printability while maintaining surface smoothness.
• Disadvantages of extremes:
• Too low: Ink drying issues; risk of smudging or offsetting.
• Too high: Paper becomes unstable, leads to warping or cockling.

 3. Cardboard (e.g., Shipping Boxes, Retail Displays)
🟢 Medium to High Vapour Permeability (Often Acceptable)

• Benefits:
• Breathability reduces condensation — useful for fresh produce boxes.
• High permeability corrugated board can be cost-effective and recyclable.
• Disadvantages:
• Not suitable for moisture-sensitive contents without liners/coatings.
• Needs barrier coatings for frozen or wet goods (wax, PE, etc.).

🟠 Low Permeability (when coated)

• Benefit: Better water resistance for cold/frozen items.
• Drawback: May compromise recyclability or print adhesion.

4. Printing onto Fabrics (Textiles, Apparel)
🔵 High Vapour Permeability (Preferred)

• Benefits:
• Maintains breathability in garments (especially sportswear).
• Essential for comfort — lets moisture escape from the body.
• Disadvantages of low permeability:
• Traps sweat — causes discomfort and potential skin irritation.
• May cause ink to flake or crack over time due to stiff barrier layers.

Sustainability Considerations

Permeability	Environmental Impact
Low (e.g., multilayer films)	Often difficult to recycle; needs special treatment
Medium (e.g., bio-coated paper)	Good balance of function and recyclability
High (e.g., uncoated paper, cellulose film)	Biodegradable but poor barrier — short shelf life

Summary Table

Application	Preferred WVTR	Why?
Food Packaging	Low	Barrier to moisture; preserves freshness
Coated Paper	Medium	Ink control, stability, print quality
Cardboard	Medium–High	Breathability vs. barrier, depends on contents
Fabrics	High	Breathability and comfort

Vapour permeability plays a critical but often overlooked role in the printing industry. Its importance varies across different types of printing, depending on the materials used, the end-use of the product, and the environmental conditions to which the printed materials will be exposed.

 

Guide to printing processes and vapour permeability

1. Lithographic (Litho) Printing

Uses of Vapour Permeability:

• Litho printing is widely used for packaging, marketing materials, and high-quality prints. Vapour permeability is absolutely crucial in ensuring that inks dry properly and consistently. It doing this it controls print quality, the sharpness, colour accuracy and the ability to bleed into the substrate.
• It affects the interaction between the printed surface and external environments, especially in food and pharmaceutical packaging where barrier properties must be maintained.

Problems:

• Reduced print quality
• Inadequate vapour barriers in substrates can lead to ink smudging or extended drying times.
• In food packaging, poor vapour control may result in contamination, odour migration or reduced shelf life.
• Delamination or warping of layered printed materials due to moisture ingress.

2. Newsprint / Coldset Web Offset

Uses of Vapour Permeability:

• Newsprint is designed for rapid production and cost efficiency. Paper used must be is highly permeable to water vapour, allowing fast drying of low-viscosity inks.
• Vapour permeability is essential to maintain press speed without compromising legibility or quality.

Problems:

• High permeability can make the paper susceptible to moisture pick-up from the environment, leading to wrinkling, expansion or misfeeds.
• Ink can feather or bleed on overly absorbent substrates.
• Long-term storage of newspapers may result in discolouration and brittleness due to environmental moisture.

3. Fabric / Textile Printing

Uses of Vapour Permeability:

• In textiles, especially for performance or wearable fabrics, vapour permeability impacts not only the print quality but also the final garment’s breathability.
• Helps control how dyes and inks penetrate and set into fibres.

Problems:

• Moisture barrier layers added to enhance durability or water resistance can interfere with ink absorption and cause print defects.
• Poor control of vapour flow during curing can lead to ghosting or inconsistent colouration.
• Incorrect permeability in fashion or sportswear printing can result in garments that trap sweat or feel uncomfortable.

4. Flexographic Printing

Uses of Vapour Permeability:

• Commonly used for flexible packaging, labels, and corrugated boxes.
• Vapour permeability of the substrate (e.g. films, foils, or coated papers) must be tightly controlled, especially in packaging for food, cosmetics, or chemicals.

Problems:

• Inadequate barrier performance can lead to contamination, or material degradation.
• Aroma or scent molecules, from food, cosmetics, detergents, and personal care items s will gradually escape if the material the is too permeable to contain these volatile molecules.
• Printing defects may arise due to vapour entrapment or uneven drying, especially on plastic or multilayer substrates.

5. Gravure Printing

Uses of Vapour Permeability:

• Used for high-volume production of magazines, decorative laminates, and flexible packaging. Also used in scratch and sniff.
• Consistency in vapour transmission helps maintain print, scent fidelity and finish, particularly on glossy or coated materials.

Problems:

• Materials with poor moisture control may expand or contract, distorting the image.
• In flexible packaging, incorrect vapour transmission rates can shorten shelf-life or compromise product integrity.
• Long print runs can suffer from cumulative defects if vapour levels are not properly managed.

6. Screen Printing

Uses of Vapour Permeability:

• Often used on a wide range of substrates including textiles, glass, plastics, and ceramics.
• Control of vapour transmission influences ink adhesion and curing.

Problems:

• On impermeable substrates like plastics or metals, vapour entrapment can cause blistering or bubbling under the ink layer.
• In textiles, inconsistent permeability leads to patchy ink penetration or dye migration.

Summary
Across all forms of printing, vapour permeability is critical in balancing ink performance, substrate behaviour, drying time, and end-use requirements. Misjudging it can lead to aesthetic flaws, functional failures, or even legal compliance issues (e.g. in food or medical packaging). This makes the ability to measure and control vapour permeability not just a technical detail, but a vital component of reliable, high-quality print production.