Reactive-wetting interface dynamics exhibits complex spatio-temporal patterns during the kinetic roughening process of the triple line. This could seemingly be described by scaling (growth and roughness) exponents. However, we show that the non-linear interface dynamics is much more complex. Using extreme value statistics, in particular the persistence measure, we demonstrate the difficulties to associate a given universality class to this complex system. Our reactive-wetting system, which is the only known system in room temperature, consists of small mercury droplets (150m in diameter) spreading on thin silver films (2000 – 4000 A). The process is monitored using an optical microscope.

In this talk we discuss the growth and roughness exponents of the propagating interface, the temporal interface width fluctuations during a single growth process, and the lateral correlation length along the triple line – all as a function of the silver substrate roughness and the temperature of the system. We then introduce the persistence measure in order to demonstrate the complexity of the system, and suggest several numerical models to obtain better insights regarding the microscopic physical mechanisms that play a role in the process.