Rheology concerns the way a material deforms and flows.
Physical characteristicssuch as viscosity, viscoelastic behavior, temperature and time dependencecan be measured. Perception is defined as the experiences caused by stimulation of thesenses. When applying a product to the skin, a person will deform the sampleand perceive the resulting texture and flow characteristics. An individualwill subconsciously assess various attributes of a sample on the skin,such as how thick or thin it may be, how hot or cold it feels and whetherit feels pleasant or not. By varying the rheology product formulators may tailor make a product toachieve a specific skin feel.