  Relaxation of initially out-of-equilibrium rough interfaces in presence of
thermal noise is investigated using Langevin formalism. During thermal
equilibration towards the well-known roughening regime, three scaling regimes
observed over three successive ranges of length-scales are evidenced: thermal
roughening (late stage) at small scales, transient smoothening at intermediate
scales and remnant of the initial conditions at large scales. A generalization
of the Family-Vicsek scaling is found for the smoothening regime. A distinctive
feature of the transient smoothening regime resides in the existence of a
super-universal exponent, i.e. independent of the considered model. This
approach allows interpreting a series of AFM images of sapphire surfaces
showing the thermal evolution of initially rough step edges.
