Colloidal control of suspension viscosity

Some very significant changes can be brought about by the alteration of colloidal conditions, since the overall force between particles can be made more attractive or repulsive in nature. We will now consider a few examples of such manipulation. 

If enough salt is added, the particles are eventually neutral with respect to one another, and just bounce off each another if they collide. The viscosity is then at a minimum. If even more salt is added, the electrostatic repulsion is swamped, the van-der-Waals attractive force dominates, and the particles flocculate. The viscosity then increases again, as in figure 19. 

In summary, we note the following colloidal factors at our disposal that we could use to change the viscosity of a given suspension - 

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