Water vapour transmission rate (WVTR) of paper or board with the gravimetric dish method

The gravimetric dish method can be used to determine the water vapor transmission rate (WVTR) of materials that have a high water vapor permeability. This method is intended for sheet materials that have water transmission rate over 1 g / m² / day. The maximum sample thickness is 3 mm. In the test, a water absorbent material is placed in a metal cup that is covered by the studied material, which is sealed to the cup with wax. The test sample is placed in a conditioned cabinet and its mass is measured. From this the WVTR value can be calculated. The method is not applicable for materials that are damaged by hot wax or shrink under the used test conditions.