The water absorptivity of corrugating medium is measured by forming a specimen into a boat shape, floating this on the surface of a vessel of water, and determining the time for the visible surface to become saturated. This method is applicable to corrugating medium as it is commercially produced by all processes. It is generally applicable to elatively unsized (water leaf) paperboards. It has not been investigated for applicability to more highly sized boards or to grades produced in different grammage (basis weight) than those normally used in corrugating medium. Two preferred methods which can be performed in the same general time period with equal repeatability are also described in TAPPI T 831 “Water Absorption of Corrugating Medium: Water Drop Penetration Test” and TAPPI T 835 “Water Absorption of Corrugating Medium: Water Drop Absorption Test.” They do not give the same numerical results, but, in general, will rank the materials in the same order as this method. Another preferred method is TAPPI T 832 “Water Absorption of Corrugating Medium: Float Curl Method.” TAPPI T 432 “Water Absorbency of Bibulous Paper” and TAPPI T 492 “Water Absorption of Paperboard (Nonbibulous)” 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.