A technique has been developed to study the differences in the nucleation and growth of metallic films during their vacuum thermal deposition. The ‘‘P’’ and ‘‘Q’’ resistance arms of a Wheatstone bridge are made equal and arms ‘‘R’’ and ‘‘S’’ are replaced by two substrates having proper contacts, facing the vapor source in the vacuum chamber. During deposition, if nucleation and growth conditions of the films on these substrates are exactly identical, no voltage difference is developed across the junctions ‘‘PQ’’ and ‘‘RS’’ of the bridge throughout the growth of the films. If, however, there is even a minute difference in the nucleation and growth sequence of these films, the critical time at which the films become conductive may be different for both the films which ultimately gives a rectangular pulse‐type signal which is recorded by the X–Y recorder. As the critical thickness at which the metal film becomes suddenly conductive is dependent on a large number of factors, e.g., flux and species of vapor, structure and temperature of the substrate, residual gas pressure and its nature, fields present on or nearby the substrate etc., this technique has potential applications in metallic thin film technology.