The degree of impregnation of an agglomerate by the suspending matrix is an important parameter because it influences the agglomerate cohesion and thus has a direct effect on dispersion mechanisms. Penetration kinetics reported in the literature were only measured in Newtonian or not very elastic matrices, although one of the main applications is the dispersion of porous filler in elastomers. The aim of this article is to study the infiltration of porous silica agglomerates by uncured elastomers using optical microscopy. The application of the model of Bohm (infiltration of a Newtonian fluid into a porous sphere) is discussed. (C) 2004 Wiley Periodicals, Inc.