The water desorption rate from various cloths humidified with humid air of various relative humidity has been measured by changing desorption time under vacuum condition. Except for initial stage of desorption, the desorption rate, which is given by the change of water content within cloth with desorption time, is proportional to water content within cloth. The desorption rate constant is small for cloth of natural fiber having hydrophilic group and large for synthesized fiber cloth especially for polyester cloth. For initial stage of desorption, apparent rate constant of desorption was determined from the change in water content within cloth, which indicates larger difference in values by species of fibers than the desorption rate constant in the following stage. On the other hand, apparent absorption rate constant, determined from the apparent desorption constant and the water content within the cloth in equilibrium with humid air, varies little with both of fiber species and relative humidity of air used for humidifying cloth, i.e., the change in equilibrium water content within cloth by fiber species or relative humidity might come from the change in desorption rate of water. Absorption rate constant for the stage following the initial stage, which is calculated with the desorption rate constant and drying rate constant reported in literature, also varied little with fiber species, and the value is about 1/3 of apparent absorption rate in the initial stage.
