This method provides for the gravimetric determination of the water vapor transmission rate (WVTR) of sheet materials at 23 degrees C with an atmosphere of 50% RH on one side and a desiccant on the other. It is generally suitable for materials up to 3 mm thick (1/8 inch), although it may be used with caution for thicker materials if the edges of the specimen are completely sealed. For testing at other conditions, see TAPPI T 464 Gravimetric Determination of Water Vapor Transmission Rate of Sheet Materials at High Temperature and Humidity for 37.8 degrees C (100F) and 90% RH. This test can be used for both creased and uncreased specimens. See TAPPI T 465 Static Creasing of Paper for WVT Tests and TAPPI UM 590 Creasing of Paperboard for Water Vapor Transmission Rate (WVTR) Testing for the creasing procedure for paper and paperboard respectively.