Viscosity is a fluid property that indicates the resistance of a fluid to either stress or movement. Materials such as rubber before cure show a reduced viscosity with increasing stress or movement. This shear thinning behavior is important to processing operations. As the shear rate is increased, the viscosity decreases so, in the case of extrusion, a doubling in throughput does not require a doubling in motor power requirements. Additionally, monitoring the viscosity of the polymers and/or compounds allows one to assess the potential for processing issues.