Definition(s)
Plastic Viscosity
Measure of the high-shear-rate viscosity which depends upon the number, shape and size of solids and the viscosity of the liquid phase. NOTE Plastic viscosity is calculated by subtracting the 300 r/min concentric cylinder viscometer reading from the 600 r/min concentric cylinder viscometer reading (see ISO 10414-1 and ISO 10414-2).
Source: API RP 13C, Recommended Practice on Drilling Fluids Processing Systems Evaluation, Upstream Segment, Fourth Edition, December 2010. Global Standards