The infiltration of polymeric liquids into carbon black agglomerates has been studied using buoyancy measurements. Both the rate of infiltration and the degree of saturation decrease with increasing matrix viscosity. The influence of interfacial chemistry was demonstrated by comparing the enhanced infiltration and saturation that occurs with polybutadiene and ethylene propylene copolymers in comparison to polydimethyl siloxane liquids. However, the differences attributable to interfacial chemistry are masked when highly viscous liquids are used. The influence of the agglomerate pore structure on infiltration and saturation characteristics was also examined. In the case of low-structure carbon black, the infiltration and saturation characteristics showed a sensitivity to packing density while the same was not true for agglomerates of the high structure carbon black.