The water absorptivity of corrugating medium is measured by floating a specimen on the surface of a vessel of water, and determining the time for the specimen to become saturated. This method is applicable to corrugating medium as it is commercially produced by all processes. It is generally applicable to relatively unsized (water leaf) paperboards. It may not be applicable for more highly sized boards or to grades produced in different grammage (basis weight) than those normally used in corrugating medium. TAPPI T 432 "Water Absorbency of Bibulous Papers" and TAPPI UM 596 "Water Absorbency of Non-Bibulous Paperboard" have been used to measure the water absorptivity of corrugating medium, but the study which led up to the development of this method indicates that they lack the repeatability of this method and most certainly take more time to conduct, especially on the more resistant samples.