The consumer who uses antiperspirants and deodorants is intimately aware of the rheological or flow properties of those products. They may not know that viscosity is the ratio of shear stress to shear rate, or that their roll-on is a thixotropic suspension, but they know the type of behavior they have come to expect from their antiperspirant. If the consumer purchases a roll-on product, he or she does not expect it to drip from the container whenever the bottle is tilted during application, but must easily transfer from the ball to axilla. Once applied, the product must stay where it was applied, and not allow gravity to pull it down the person’s side. After passing these tests, the consumer quickly finds out whether or not the formula is tacky or sticky. The rheological expectations of stick and aerosol products are equally demanding. Does the stick apply evenly and effortlessly? Does the aerosol product leave a “cloud” hanging in the air, or does most of the product go where it is intended to, and stay there.