ABSTRACT
MARCO BRUGNARA, 1·* CLAUDIO DELLA VOLPE, 1 DEVID MANIGLIO, 1 STEFANO SIBONI, 1 MARTINO NEGRI2 and NADIA GAETf 'Department of Materials Engineering and Industrial Technologies, University ofTrento, Via Mesiano 77, 38050 Trento, Italy 2CNR IVALSA, Via Biasi 75, 38010, S. Michele al/'Adige (TN), Italy
Abstract-From the 1980s, the computer controlled Wilhelmy experiment has been the common method to measure contact angles. The typical samples have parallelepiped shapes and are relatively 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, wood or nonwoven fabrics the results can be doubtful because of significant absorption of the test liquid and swelling of the sample. In the present paper a 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 it produces consistent results. Some experiments are presented and analysed for calcareous stones, different kinds of woods and non-woven fabrics. A companion paper explores the possible use of the Washburn equation in estimating the contact angles.
