Water vapor permeability test

*Water vapor permeability of fabrics can be basically measured by the desiccant ( drying) method or the water method. 

*The water method is described here. 

*A sample is placed and sealed to the open mouth of a vessel containing water. 

*This is then placed in a controlled atmosphere. 

*Air gap between the sample and water is maintained. 

*The weight loss with time is used to determine the rate of water vapor migration.