The paper describes a dynamic model to simulate expressive wrinkles in 3D facial animation and skin ageing. A skin surface is defined that can slide over an underlying layer, which constrains the surface by a spring force that simulates the connective fat tissue between them. Muscle masks are constructed to characterize the muscular contractions that provide the facial movement. Skin deformation is simulated through an elastic process assembled with visco and plastic units. By adjusting parameters for this physically based model, distinctive wrinkles for different faces can be generated