The TAPPI T 433 standard specifies a test method for water resistance of sizing paper and Cardboard, using the dry indicator method. This method is based on Carson's dry indicator method and subsequent improvements, and evaluates the water resistance of the paper sample by measuring the time it takes for water to penetrate. This method is suitable for materials with short test times (within about 30 seconds), especially loose sizing paper, not hard sizing paper or Cardboard. The test results can be used to evaluate the water resistance of paper and Cardboard when exposed to water, providing an important reference for quality control and application of Encasement materials.