Sliding touch is one of the key inputs for the perception of materials in our environment. We are interested in the contribution of fingertip friction to the process of tactile exploration and perception. Psychophysical studies address correlations between subjective judgements of perception and measured physical parameters of interactions, in our case of friction on materials with systematically varied surface structure. A challenge in this approach are large variances in skin physiological parameters between the participants in our studies. I will discuss how surface structures are perceived in sliding touch, for which materials the determination of physiological parameters is helpful to predict friction, and if humans are able to rank friction differences correctly. Materials range from 3D printed plastic over micro-structured rubber to honey.