MEASUREMENT OF FOAM VISCOSITY BY INDENTATION

The force-displacement curves for the penetration of a commercial shav ing cream foam by a vertical circular cylinder were obtained using a v ery sensitive tensile machine. From these results, the (apparent) visc osity, mu, of the foam was calculated. The effects of the velocity of indentation, of the radius of the indenter and of the radius of the cy lindrical vessel which contains the foam were experimentally studied. A theoretical analysis of foam indentation was undertaken under the as sumption that the foam behaves as a power-law fluid; i.e., the foam vi scosity, mu, has a power dependence on shear rate, gamma, with mu prop ortional to gamma ((n-1)). This hypothesis describes well the experime ntal results and the power law exponent found was n=0.56.