The present invention relates generally to methods for characterization of fluids, and, particularly, to methods of determining an interfacial tension between a first liquid and a second fluid, the method comprising the steps of: (a) introducing the second fluid into the first liquid at a constant flow-rate so as to cause the second fluid to periodically form successive droplets or bubbles; (b) recording a heat change of step (a) as a function of time, obtaining a periodic heat versus time profile; (c) obtaining the period of the heat change recorded in step (b); (d) providing a calibrated relationship of the interfacial tension as a function of period for said constant flow-rate and said second fluid; and (e) correlating the period obtained in step (c) with the calibrated relationship, and determining the interfacial tension between the first liquid and the second fluid for said constant flow-rate.