An improved sessile drop technique was used to measure the changes in contact angle of a reaction system (Al/MgO). By plotting the results on a logarithmic time scale, the authors arrived at a new understanding of the wetting process. It was found that the contact angle progresses through three phases and that it is necessary to adopt the values of phase II in order not to overestimate wetting. The relationship between interface diameter and contact angle was investigated and the conditions characterizing wetting increase were defined.