Velocity-Gradient Methods in Rheology

Since in a colloidal or quasi-plastic material, the viscosity is a function of the rate of shear, it seems best to determine the velocity-gradient across a section perpendicular to the direction of flow under shearing forces, and to determine the coefficient of viscosity under a given velocity gradient. An account is given of the experimental methods at present available for this purpose, and a method indicated by which the viscosity may be calculated from such measurements. The viscometers described comprise instruments based on the optical, electromagnetic, hot-wire and colorband principles, respectively.