Wettability of porous materials, 1: The use of Wilhelmy experiment: The cases of stone, wood and non-woven fabric

Abstract-From the 1980s, the computer controlled Wilhe1my experiment has been the common method to measure contact ang1es. The typical samp1es have parallelepiped shapes and are relative1y flat and homogeneous, and the test liquids are not very viscous. Some results have been published for more complex and asymmetric shapes or for more complex experimental situations. However, one of the commonest difficulties in experiments using porous samples is the absorption of the liquid. In the case of porous stones, w o od or nonwoven fabrics the results can be doubtful because of significant absorption ofthe test liquid and swelling ofthe sample. In the present papera new procedure is presented for correctly using the Wilhemy experiments on porous samples. The method consists in simple modelling of the Washburn-like mechanism of absorption and i t produces consistent results. Some experiments are presented and analysed for calcareous stones, different kinds of woods and non-wo.ven fabrics. A companion paper explores the possible use ofthe Washburn equation in estimating the contact angles.