A nucleation and growth mechanism is proposed for the formation of the reaction product at the interface between polycrystalline alumina and liquid-metal alloy drops containing titanium. The reaction product had been previously identified to be an oxide of titanium. The growth of reaction product islands was clearly observed at the alumina-metal interface using optical microscopy after dissolving the metal droplets with acid. The fractional coverage was quantified as a function of time and, by assuming Avrami-type reaction kinetics, surface reaction rate constants, k, were calculated for copper-titanium and silver-titanium alloys on alumina. Reaction rate constants between 1.4 x 10(-4) and 18 x 10(-4) s(-2) were obtained for copper-titanium alloys on alumina. The k values for silver-titanium alloys were found to be an order of magnitude lower (2.5 x 10(-6) and 7.2 x 10(-6) s(-2)) then the k values obtained for copper-titanium alloys on alumina.