A test used to measure the water resistance of paper, or the adequacy of its sizing, in particular, the time it takes for a liquid to completely penetrate the paper. A powder containing a water-sensitive dye is sprinkled on one side of a paper sample, and the reverse side of the sample is floated on water. The amount of time between the paper initial contact with the water and the appearance of the pronounced color of the indicator dye is the time it takes water to penetrate the paper.
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