Predicting subjective spreadability, viscosity, and stickiness.

Subjective spreadability, viscosity, and stickiness perceived with the fingers were predicted from fluid mechanics. The correlation coefficients of these predictions were 0.95 for spreadability, 0.95 for viscosity, and 0.09 for stickiness. The two important assumptions in the predictions were that spreadability and viscosity were perceived as shear stress and that stickiness was perceived as time. When the finger geometry was approximated as two parallel plates, the predictions only required rheological data for the Newtonian and non-Newtonian liquids used. While these liquids covered a range of 10-6 in apparent viscosity, large variations in other fluid properties such as density and surface tension were not studied.