We elucidate the basic physics of shear thickening in colloids from the viewpoint of the dissipative interactions between close approaching particles. With just hard-sphere lubrication, Brownian spheres show a logarithmic thickening at high stresses. We use a model of interactions due to porous surfaces to show that thickening is enhanced by stronger dissipative surface forces, and compare successfully simulation with experiment. The onset of thickening is sensitive to the degree of order and history of shear.

• Received 17 August 1995

DOI:https://doi.org/10.1103/PhysRevLett.77.4660