The rate of capillary wetting in fibrous assemblies was measured using newly developed apparatus. The change in electric conductivity with time was measured using a plug of fiber, fabric, or filter paper in a cylinderical Teflon cell 10 mm in inner radius and 3 mm or 7 mm in height. The electrodes were platinum disks 16 mm in diameter with 37 holes each with a radius of 0.5 mm. They were placed at the top and bottom of the plug. The head of the wetting liquid was adjusted to the bottom level of the plug and the liquid rose by capillarity. The traveling time in the shortest capillary in the fibrous assembly, t0, is detected as the yield value in the electric conductivity versus time curves, and the initial slope of the curves, S, were used as parameters of the wetting rate. The increase in t0 and decrease in S was indication of decrease in the capillary wetting rate for the plug. Measurement of capillary wetting rate by this apparatus was successfully carried out using plugs of cellulose filter paper, polyester fabric, and nylon fiber.
