Sample specimens are conditioned and measurements made in a standard atmosphere laboratory (70 ± 2°F and 65% RH).
The rate of moisture vapor diffusion through the material is determined according to the Simple Dish Method, similar to ASTM E96-80. As pictured, a sample is placed on a water dish, allowing an air space between the water surface and test specimen. A vibration free turntable carrying 8-12 dishes rotates uniformly at set rate to ensure that all dishes are exposed to the same average ambient conditions during the test. The assembled specimen dishes are allowed to stabilize for two hours before taking the initial weight measurement. They are weighed again after a 24 hour interval. These measurements are then used to calculate the rate of moisture vapor loss (MVTR) in units of g/m2-24 hours. A higher MVTR value indicates there is a greater passage of moisture vapor through the material.