Rheological evaluation of sensory attributes of lipstick

Sensory attributes of lipstick were evaluated by measuring the strain dependence of storage modulus (G') and dissipation factor (tan delta) of the lipstick sample that was kneaded by a newly developed method (Petri dish method). First a sliced lipstick peace set between two glass plates was squeezed by pressing on the upper plate and then kneaded by moving the upper glass plate to and fro while holding the lower one. Rheological parameters relating to the sensory attribute during the coating of lipstick were obtained by measuring the sample only squeezed, while the one relating to the sensory attribute after the coating was obtained by measuring the sample kneaded to and fro ten times. The lipstick having strong protective film feeling, which was perceived existence of protective film on the lip, showed a characteristic strain dependence of tan delta, showing a peak spreading over the measured strains. It was found lipsticks giving this tan delta peak clearly had stacking structure of wax crystals in its coated film.