68 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS 5 10 15 20 Frequency, Cycles per Second x 10 2 Figure 6. Storage modulus of aerosol foams as a function of cross-head movement frequency. O, Flavor variant no. 1. [•, Flavor variant no. 2. 2O eq 16 m 14 • 12 0 ...q lO 5 10 15 20 Frequency, Cycles per Second x 10 2 Figure 7. Loss modulus of aerosol foams as a function of cross-head movement frequency. O, Flavor variant no. 1 [], Flavor variant no. 2.

SHAVING FOAM VISCOELASTIC PROPERTIES 69 o 10 i c- 4 .-- 5 10 15 20 Frequency, Cycles per Second x 10 2 Figure 8. In-phase viscosity of aerosol foams as a function of cross-head movement frequency. •, Flavor variant no. 1 [], Flavor variant no. 2. springs and dashpots representing the elastic and the viscous components of the system, respectively (7). Our results appear to fit the Voigt model (Figure 10), which is composed of a dashpot and a spring connected in parallel. The values of the storage and the loss moduli of the Voigt model can be expressed as: G'(co) = Go (13) (.o 15 •10 o '• 5 o 5 10 15 20 Frequency, Cycles per Second x10 2 Figure 9. Out-of-phase viscosity of aerosol foams as a function of cross-head movement frequency. Flavor variant no. 1 {•, Flavor variant no. 2.