The aim of this investigation is to study the mechanism of spontaneous infiltration of AlSi alloys into porous graphite with emphasis on the role of the reaction of carbide formation in the infiltration process. Results are obtained using the sessile drop technique that enables the variation of the infiltration depth with time to be monitored in situ. In addition to the infiltration data, this method provides quantitative information on wetting thus allowing the values of wetting and infiltration rates measured in the same experiment to be compared.