Experimental Interpretation of Interfacial Separation and Squeezing   Pressure
  The logarithmic relation between interfacial separation and squeezing pressure between randomly rough surfaces, has been predicted by both theory and experiment. However, the experimental slope between interfacial separation and logarithmic squeezing pressure, is slightly bigger than that predicted by theory. Here we present a detailed explanation on the slope difference between theory and experiment. 
C. Yang, B.N.J. Persson, J. Israelachvili and K. Rosenberg