We thought it would be good to follow up on some of the issues raised in Elizabeth's talk last week. One issue is clearly whether changes in contact area with time are coming from subsurface plastic deformation, changes in interfacial energy with time in contact, capillary condensation, recoverable viscoelastic deformation, etc.. The answer may depend on the material system. To kick off the discussion Jay Fineberg will show some hysteretic measurements of contact area with load for PMMA that don't show evidence of permanent plastic deformation. Then Patty McGuiggan will show some hysteresis curves with discrete jumps that are humidity dependent, but appear to be friction related.