Introduction

ASTM E96 is a widely recognized standard developed by the American Society for Testing and Materials (ASTM) that outlines 

test methods for determining the water vapor transmission (WVT) properties of materials. This standard is essential in

 industries such as packaging, construction, textiles, and medical devices, where controlling moisture permeability is 

critical for product performance and durability.

Purpose of ASTM E96

The primary objective of ASTM E96 is to measure the rate at which water vapor passes through a material under specified 

temperature and humidity conditions. This property, known as water vapor transmission rate (WVTR), helps manufacturers 

assess how well a material can resist or allow moisture passage—an important factor in applications like food packaging,

 building insulation, and protective clothing.

Testing instruments:WVTR-C6 Water Vapor Permeability Tester

Test Methods in ASTM E96

ASTM E96 provides two principal test methods:

Desiccant Method (Dry Cup)

The test specimen is sealed over a dish containing a desiccant (drying agent) and placed in a controlled-humidity environment.

Water vapor moves from the humid chamber through the material into the dry desiccant.

The weight gain of the dish over time determines the WVTR.

Water Method (Wet Cup)

The dish is filled with distilled water, and the specimen is sealed over it.

The assembly is placed in a dry environment, and water vapor passes through the material into the surrounding air.

The weight loss of the dish is measured to calculate the WVTR.

Each method is suited for different material types, depending on whether the material is more permeable to moisture from a

 humid or dry environment.

Key Factors Influencing Test Results

Several variables can affect the accuracy of ASTM E96 testing:

Temperature and Humidity – Controlled test conditions are crucial for reproducibility.

Material Thickness – Thicker materials generally exhibit lower WVTR.

Sealing Integrity – Any leaks in the test setup can lead to inaccurate results.

Airflow – Stagnant vs. moving air can influence vapor transmission rates.

Applications of ASTM E96 Testing

Understanding WVTR through ASTM E96 helps in:

Packaging – Ensuring moisture-sensitive products (e.g., food, pharmaceuticals) remain protected.

Construction – Evaluating building materials like vapor barriers and insulation for energy efficiency.

Textiles – Assessing breathability in fabrics for sportswear and medical garments.

Electronics – Preventing moisture damage in sensitive electronic components.

Conclusion

ASTM E96 is a critical standard for evaluating water vapor transmission in materials, providing essential data for product 

development and quality control. By selecting the appropriate test method and maintaining strict testing conditions,

manufacturers can optimize material performance for various applications.

For more detailed procedures, refer to the latest version of ASTM E96 from the official ASTM International website.