A phase-separated mixture of cyclohexane and acetic anhydride was subjected to positive linear temperature ramps while the capillary rise of the acetic anhydride–rich phase against a glass substrate was measured. The ramps, which drove the system out of thermal equilibrium, had the effect of producing large nonlinear changes in capillary rise with respect to ramp rate. These changes may be explained in terms of the nonequilibrium behavior of the wetting-layer thickness, and depended only weakly on the size of the ramps. The deviation of the capillary rise from its equilibrium value was found to attain a steady state after the temperature had been raised by ≊0.6 K from the starting temperature of ${\mathit{T}}_{\mathit{c}}$-T=5.9 K, independent of the ramp rate. This steady state may be indicative of the virtual disappearance of the wetting-layer. Unlike recent direct observations of wetting-layer thickness [Dean Ripple and Carl Franck, Phys. Rev. A 44, 8289 (1991)], our results could not be simply described as the ‘‘equilibrium’’ wetting behavior of a bulk nonequilibrium experiencing linear response to a weak temperature ramp.

• Received 12 January 1993

DOI:https://doi.org/10.1103/PhysRevE.47.3497