The shear stress is the force F per area A needed to move a material. For materials with different flowing resistance, different forces are required to move the material at the same speed. The smaller the area, the lower the force required to move the material at the same rate, and vice versa. (Example: painting with wide versus narrow brush).  

The shear rate  (formerly D) is the ratio of the velocity v to the distance d. If a material is applied (coated) at the same velocity but with different film thicknesses, this results in different shear rates. The lower the coating thickness, the higher the shear rate and vice versa.

The shear rate  (formerly D) is the ratio of the velocity v to the distance d. If a material is applied (coated) at the same velocity but with different film thicknesses, this results in different shear rates. The lower the coating thickness, the higher the shear rate and vice versa. The measured values in the low shear range characterize the properties of a material, during storage (storage stability/settling behavior) and after application (sag resistance and leveling). In the medium shear range, the measured values characterize the so-called in-can viscosity, the viscosity of the material in the container under moderate stirring by hand. The quality control for a viscosity is usually carried out in this range. The measured values in the high shear range characterize the viscosity of the material during application and during production and filling. 

Viscosity is defined as the quotient of shear stress and shear rate . It is the measure of resistance to flow.

A Newtonian fluid is characterized by the fact that its viscosity is always the same, regardless of the stress applied. Its viscosity is a material constant.

Characteristic of a structural viscous - also called pseudoplastic - flow behavior is a high viscosity at rest (storage), which decreases with increasing shear stress (shear thinning) and immediately builds up again with decreasing shear stress.

Thixotropic flow behavior is shear-thinning. The viscosity builds up again with time delay after shear stress is removed. 

A special feature for shear-thinning substances can be the formation of a yield point. In this case, the internal structure of the substance is so strong that the substance is deformed before flow can occur, despite the applied force. Only if the applied force is strong enough that the internal structure is destroyed does the flow begin.

The measured values in the low shear range characterize the properties of a material, during storage (storage stability/settling behavior) and after application (sag resistance and leveling). 

In the medium shear range, the measured values characterize the so-called in-can viscosity, the viscosity of the material in the container under moderate stirring by hand. The quality control for a viscosity is usually carried out in this range.

The measured values in the high shear range characterize the viscosity of the material during application and during production and filling.