The viscosity of many dental materials decreases with increasing strain rate until it reaches a nearly constant value. That is, the faster they are stirred, forced through a syringe, or squeezed, the less viscous and more fluid they become. This is pseudoplastic viscosity and is illustrated by the change in slope of the plot in the figure. The viscosity of a pseudoplastic fluid decreases with increasing shear rate.  The tomato-based food condiment ketchup is also pseudoplastic, which makes it difficult to remove from a bottle. Shaking the bottle or rapping the side of the bottle increases its shear rate, decreases its viscosity, and improves its pourability.    A Bingham plastic is a viscoplastic material that behaves as a rigid body at low stresses but flows as a viscous fluid at high stress. It is named after Eugene C. Bingham who proposed its mathematical form.