In pressing, shear is the dominating component of the deformation, but it is often accompanied by a significant level of extension. The balance between shear and extension depends on the geometry, as well as on the boundary conditions. For example, shear will often dominate under the adhesion condition, while elongation may play a significant role under full slipping.

Since shear is often the main deformation component that develops in this process, knowledge of the shear viscosity of the material is necessary. While shear rates can be high, the overall deformation usually remains moderate. A Cauchy strain of the order of ten is a reasonable order of magnitude.